Could you tell me the reasons why you can't access gmail?

I am unable to log into my gmail account. There's no error message is displayed but I have a blank screen. Also, when I try to login to my YouTube account, the log in page fails to open. I can access both in Chrome but not Firefox. I have used Firefox for years and was my default browser. Unfortunately I've had to change it to Chrome.

What version of your Firefox?

I am unable to log into my gmail account. There's no error message is displayed but I have a blank screen. Also, when I try to login to my YouTube account, the log in page fails to open. I can access both in Chrome but not Firefox. I have used Firefox for years and was my default browser. Unfortunately I've had to change it to Chrome.

try this:

https://support.mozilla.org/en-US/kb/how-clear-firefox-cache

Mac OS 10.13.6 Firefox 87.0 (64-bit)

I've tried restarting my Mac (several times), refreshing Firefox, Starting up in safe mode, opening a private window, clearing my cache, Clearing start-up cache, completely uninstalling Firefox and then reinstall from scratch. I've removed Avast Security VPN....