Gmail works only with basic html version

recently it stopped working properly (stuck on login page) but it's rlly simple and quick to check , send, reply and delete emails.

Said cookies ares disables while in Firefox cookies are allowed.

Doesn't work, says (roughly translated):
400. Error
The URL wasn't found on the server.

Installed, but doesn't do anything. Following error:

"400. That’s an error.
The requested URL was not found on this server. That’s all we know."

I thought maybe there is a setup process. But, no. Couldn't find any kind of setup.

This is a waste.

Doesn't work, says (roughly translated):
400. Error
The URL wasn't found on the server.

Так и не нашел как переключить режимы отображения писем GmaIl с базового вида на простой и обратно.

Incluye publicidad, un banner enorme apenas la instalas.

After click on a specific E-Mail the mail doesn´t open. It is just empty without any content. The Add-ons is only usefull for checking incoming E-Mail, but not for open or reading it. :(

This addons seems really usefull, but I - like many people in these comments - have clicked on html view and would like to know, how to revert this setting.