Based on my knowledge, I don't think that Physics and Maths Tutor has permanently banned you from accessing their website due to an ad-blocker. I use an ad-blocker and I can use PMT without any issues. What's more likely, however, is that there could be other reasons causing the issue you are experiencing, such as an outdated browser. Try the following steps and see if these work:
1. Clear your browser cache and cookies and try accessing the website again. If you do not know, search it up in Google.
2. Try accessing the website using a different browser, such as Chrome or Firefox. I'm sure Mac devices have a Mac client version of Chrome.
3. Check if your internet connection is stable and if there are any issues with your network or router. It's best to check anyway.
4. Update your browser to the latest version to ensure compatibility with the website.
5. If the issue persists... rip.