Been using Grammarly for about a year without an account and have found it OK. I say OK because it works nice, but not any better than the built-in spell checker in Firefox.
Grammarly is slower and would often appear to be working but wasn’t. This meant I had to double spell check posts online.
The latest update which ‘I think’ landed around 14th Dec doesn’t seem to spell check, and a new pop-up comes back on every page upload. Guys, this isn’t going to help me sign-up to your service!
Grammarly assumes users are only going to use its service to fix errors. Its developers did not take into account that some users like to correct the text by retyping the correct word or manually deleting the incorrect characters.
As suggested by other members you can try to uninstall and install back the plugins. Otherwise you can visit Grammarly support: https://support.grammarly.com/hc/en-us