UPDATE:
I am updating again to 5 stars in good faith that the developer has fixed the issue. This really is a great add-on.

Original Review:
Loved this add-on until yesterday. Everything disappeared (page with my links, icon). From reading other reviews it appears that it will work again if I uninstall/re-install add-on, but big bummer to lose my tabs. I got to rely on it a little too much. Now I will know that it is much more of a temporary holding pen.

Giving this a 3 star because its a great product, however their latest update really botched everything. For people looking for a permanent solution unlike the disabling it and re-enabling it (only works until you restart Firefox), you can first back up your tabs using the methods many other reviews have outlined, then scroll down the OneTab page to the More Information section. Here you can click on the link to previous releases, uninstall OneTab and then install version 1.29 and restart Firefox. You may also want to disable automatic updates in the extension settings so it doesn't update again, and this WILL clear any tabs you have loaded in it, so remember to back up the folder before restoring it afterwards. Hope this helps and doesn't get buried instantly.

Hi, as other users also reported, tabs winddow and icon are gone and only reappaer after deactivation followed by reactivation of onetab. Furthermore, I suffer from the missing dark mode. Onetab is the only light window in my firefox which dazzles me. To create a dark skin would be as simple as adding an appropriate css file. On github e.g. an OneTab-Night-Mode is already available but is is not possible to modify an extension due to certificate restrictions by Mozilla. I am afraid I have to abandon the onetab extension for this reason. Nevertheless, the ideas behind this extension is still very good. Regards

After reboot Firefox, button OneTab becomes inactive. https://i.imgur.com/Bp7uMtM.jpg Disabling-enabling helps, but before rebooting.
P.S. Thanks for the correction!

all tabs gone, disenabling and then enabling the addon again resolved the problem

I lost OneTab button on the top left of the window and in addition, the tab list page displayed nothing.

I turned off (not deleted) OneTab, restarted the firefox, and turned on OneTab. Then all came back in my case.

Also, URLs of the tabs seems to be written in extension@one-tab.com, which is a subdirectory (subfolder) of the directory (folder) of firefox or mozilla.

I'm glad if this helps you.

Loved this add-on up until the last 24 hours. The tab close on itself. When I tried to restore the closed tab nothing was there. NOTHING! Poof gone. Blank page. Oh, and this only happening on Firefox. All seem OK on Chrome. There is no back up or way to save anything when something like this happens (and this is not the first time). If you knew you're system was about to crash a heads up would have been FANTASTIC so we could have at least exported the URL. What gives?

*Thanks for your response, but that doesn't recover everything lost because of this "bug".

I've lost all my tabs! fack you!
A temporary solution for windows: go to C:\Users\XXXX(Username)\AppData\Roaming\Mozilla\Firefox\Profiles\2vl8majd.default\extensions and open extension@one-tab.com.xpi with firefox. Then reload the tab.

This is a must-have extension for avid Internet users. The problem is that the recent update caused the extension to stop working, and I lost all my tabs. It seems that many users suffered the same thing.

I'm also a developer and I just can't imagine shipping a new product version that breaks everything so drastically.

Lesson learned. Never depend on any tool. Tools can be wonderful, but you never know when they are going to break.

tmd,This rubbish, I have lost all my labels

Re-evaluating my review. The developers have been in contact and seem to have fixed the issue.
There might be a need for a automatic backup feature that makes a backup every week or perhaps prior to an update occurring in case something goes wrong. Many users lost very important info and I can't imagine what it was like for them!

When it works - its the best thing for productivity. Backing up your data is no longer doable, the company is totally unreachable and on the Sept 16 2020 update - ext is botched and unusable. All my data - not accessible. Hopefully they issue an update in the next 24 hours.

Sept 23-Thanks for that update! Really appreciate it.

I have been using One Tab for more than a year and it's fantabulous. I don't know how I managed without it. Thanks!

OMG, I was so dependent on this add-on, it is a must, but for what I assumed it update auto and a lost more than 1000 tabs needed for work and researching, is there a way to recover them? Even onetab page extension isn't working.

Edit:
this is how I got it working on firefox on POP_OS!, got to "/.mozilla/firefox/mbmm1a9s.default-release/extensions/" on my home folder and double click on "extension@one-tab.com.xpi" file, then it opened in firefox and gave permission to the onetab notification and voilá, it restored all my tabs again!

now backing up the urls to a txt file in nextcloud using the export function

They seriously need a more robust solution for saving data or backing it up to Nextcloud or smth!

I am now very dependent of OneTab. It saves so much RAM and organizes all my open tabs nicely. To my horror this morning all my saved tabs were gone. After hours searching for a solution I find here in the reviews that the solution is to disable and re-enable the plugin to make it come back with all saved tabs. I will give 5 stars if this marvelous plugin could make automatic backup copies of all saved tabs in a simple, plain .html file that is available immediately in case of some failure either from the browser or the extension.

1.36 on FF 80.0.01 lost all tab after restar,tested in two pc ，don't upgrade.This is the second time I have lost all tab, I will not use this plugin again

Muy buena aplicación pero debería de tener la opción de sincronzar las pestañas guardadas en los diferentes navegadores donde se utilice onetab.

This extension is invaluable to me. I was afraid that all of my tabs were gone with the last update. As others have pointed out, simply disabling and reenabling the add-on should fix the problem.

Works well. Does the job. Lost the tabs once but who knows. As for people complaining about the latest update 16/9 you just have to disable and re-enable to app to function..

The last update has a bug. I solved it by deactivating the extension and activating it