That is confusing so how is firefox a grammarly problem?

When I use grammarly in any other browser it functions normally, but it does not function at all in Firefox.

I would first use the browser built spellchecker without other checkers to be sure there isn't a conflict with spellcheckers. I don't install such checkers and other Browser I use doesn't have issues with spellchecker corrections.

Hi TOEIC-Master, did this problem just start recently, or has Grammarly never worked for you in Firefox?

Some extensions do not work properly if you enable automatic private browsing mode. On the Options page, under Privacy & Security, History section, this can be triggered by setting "Never remember history" or "Always use private browsing mode". I don't know whether Grammarly is compatible with that setting.

I don't have Grammarly installed, so I'm going to suggest looking for error messages in Firefox's Browser Console. This is to some extent a land of obtuse and unhelpful messages, but hopefully we can use the filter to get something out of it.

You can open the Browser Console in a popup window using either:

• "3-bar" menu button > Web Developer > Browser Console
• (menu bar) Tools > Web Developer > Browser Console
• (Windows) Ctrl+Shift+j

Above the messages, there is a bar that should say Filter output in light letter (form field placeholder). Type grammar there and see whether anything is still left.

Leave this window open and go back to your Firefox tab and try to engage with the extension to make it do its thing. Then check for messages. Anything?

You might also try disabling and re-enabling the extension and see whether that generates any info. For that, you could use a different approach: on the Add-ons page, disable Grammarly; then in the console, clear out the filter bar and click the trash can to flush the existing list; then in Firefox, re-enable Grammarly, then check the console for any messages that could be related to starting it up.