I love LastPass, but it doesn't always fill out forms correctly. Not it's fault, probably due to web designers making forms in non-standard ways. I used to be able to just copy the password from the LastPass extension and then paste it in. HOWEVER, using the latest Firefox (57) and this version of the extension, that is no longer possible. The best workaround is to select to edit the entry in LastPass, go to that edit page, click to view the password, copy it there, close that window out, then paste it into the form.

I tried this with the latest official release of LastPass, and the beta. Same in both.

I'm sad to say that LastPass is so important for my work that this has actually made me not able to use Firefox as my primary browser. I hope that they add this functionality back in soon.