Add Blocking
HI, I read the UK Mail Online Newspaper but this has just recently blocked readers who use an ad blocker. I have even tried disabling adblock plus but it still will not allow you to read articles.
Alla svar (3)
try to remove cache of that website and disable AdBlock extension
It isn't possible to remove the 'cache' for a particular website. You may have to contact the website if that's possible. Adding a website as 'trusted' has made no difference to one website I have attempted to visit.
You could try creating a separate profile for viewing that site and install no ad blocker in that profile. It is possible also that Enhanced Tracking Protection is causing a problem so you could try disabling that on the website (click the shield icon at the extreme left of the address bar and switch the ETP button off).
https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles
https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop