The internet is a very complex place these days, with proxies, edge networks, geographically diverse hosting (meaning one region could be down while another is fine), etc.
A few things people can try to see if there is some external issue (to their own computers), vs. some issue with their computer:
1. Try using a VPN for a short while. A VPN will change the IP address used to reach the internet, and potentially also your effective geographical location. If there is a regional issue, or if there is some kind of edge network issue (i.e. CloudFlare thinks your IP is a "bad actor"!!), then this could at the very least let you know if that's the case, and give you an option to get around the problem.
2a. Try an alternative DNS service. OpenDNS is one such option, there are others. You would have to do a bit of research (AI like Claude can help here) to understand where to put the DNS server IP addresses. This could get you around some localized issue with DNS servers (I think one person mentioned they had a problem like this with their ISP on a regular basis.)
2b. Try using "DNS over HTTPS" which is an alternative method to retrieve DNS information. (DNS, domain name service, is a foundational way things on the internet find other things by human-friendly names!) This may allow you to bypass standard DNS, and if that's the issue, your issues might go away. ALTERNATIVELY, check if you ARE already using DNS over HTTPS, and if so, try DSIABLING it to see if that fixes any issues.
A few things to try if the above still don't work, which might help if the issue IS local to your computer:
1. If you are not real computer savvy, but you've tried to do things to fix your problem that are outside of your comfort zone (and particularly if you have any issues with clicky things with tails), you may have inadvertently disabled caching for certain web sites. In most "chromium" based browsers (which, at this point, is pretty much all browsers EXCEPT Safari and Firefox!), you can try the following:
a. Right-click in a blank(ish) area of the page, and choose "Inspect Element"; Alternatively use the browser main menu, go to "Developer -> Developer Tools".
b. In this, which will usually appear as a panel to the right of the current page, near the top of this panel find the "Network" tab and click it.
c. In the row of buttons and controls just below the tabs, find "Disable cache". If it is Checked, then you want to UN-CHECK it!
d. Next to the "Disable cache" is a "simulated speed" option. It should say "No throttling", if it does NOT, then change it TO "No throttling"!!
2. Also clear all data for a problematic site (like penturners.org), so that the site is at a true "clean slate" state, and try logging in again.
a. Follow previous instructions to open developer tools.
b. Find the "Application" tab and click it.
c. In this area, find the "Clear site data" button. Next to it is an option to include third party cookies. Enable that! Below, check ALL of the options: Unregister Service Workers; Local and session storage; IndexedDB; Web SQL; Cookies; Cache storage. CLICK THE "Clear site data" BUTTON!
d. This WILL log you out of the site. You will need to log in again. This should, however, truly reset you back to "honest ground state" for the site again. If you have not followed step 1, do so before you reload the site!
These should help to get you past any browser-based issues on your local computer that might be slowing things down. If these do not help, then, there is some other more abstract or obscure issue and I can't help you further.