Hi patdefranchis, If you are being logged out while you are working in the Sheet, then I would suspect something on the Google side is amiss. I found this article How to make google spreadsheet refresh itself every 1 minute? which might prevent that from happening.

Thank you very much, My_Cheese_Is_Slippin' I will read the article and try it. I hope it solves the problem. I really appreciate your suggestion.

I followed the directions and it remains the same. The message I receive is as follows: "You have logoff the account. The session has been closed. You must log in again to save the changes made to this document " I add some more information in case someone comes up with what may be happening. Before asking here I was trying to find an answer by searching on Google. I read in a forum that someone suggested trying to login Google sheets in incognito or private mode and see if the problem persisted. In private mode it does not happen. I thought maybe some addon could be responsible, but Firefox now allows us to run the addons in private mode and besides, I haven't installed any lately. There is nothing I have done coincidentally with the beginning of this problem. I have no idea why the problem started. I tried to clear cache but it doesn't solve it either. Thank you very much for taking the time and trying to help me. If I can't find a solution, I will continue working in private mode.

Do you use Ghostery? See this forum post: Google drive keeps signing me out

No, I don't use Ghostery.

Hi patdefranchis, If you Cleared cookies and site data you could try Firefox's Safe Mode to see if any of your extensions are causing the problem.

Safe Mode temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes) that might be causing problems.

Check for extensions which are not selected to work in Private windows.

This issue can be caused by corrupted cookies or cookies that are blocked.

• check the permissions for the domain in the currently selected tab in "Tools -> Page Info -> Permissions"

Clear the Cache and remove the Cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Remove the Cookies" from websites that cause problems:

• Options/Preferences -> Privacy & Security
  Cookies and Site Data -> Manage Data

"Clear the Cache":

• Options/Preferences -> Privacy & Security
  Cookies and Site Data -> Clear Data -> Cached Web Content: Clear

I followed your instructions, and also tried what My_Cheese_Is_Slippin' had suggested, but unfortunately nothing work out.

I will continue working in private mode, till I find a solution, I hope so.

I thank you very much