I haven’t had these issues, but I know others have and it really can be frustrating.
Nearly all the problems of this nature are related to your browser.
Some sites are particularly sensitive to the cookies/cache/website data stored on your device. If they make even the slightest change on the site (usually a change we don’t even see) it can cause your existing cookies/cache/data to stop “communicating” properly with the site.
Unfortunately, this website is one of the sensitive ones, and I don't see that ever changing.
The very best, basic, first-line-of-troubleshooting steps are these:
1 — Have at least 2 browsers installed. If there’s problem with one, log in with the other one and see if the identical thing happens. (IE is having more and more problems and they’re not being as well-supported as they used to be, so your best best is to avoid that one, in my opinion.)
2 — Be sure you have the most current version of the browser.
3 — a. Delete cookies/cache/website data
b. Close browser
c. Relaunch browser
I do this at least once a day with all my devices and it’s well worth the couple of minutes it takes.
4 — If there’s still a problem, be sure any addons/extensions or plugins (things like AdBlock, Adobe Flash Player, etc.) are up-to-date and that you haven’t recently changed their settings in a way that might affect interaction with this site.
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Shutting down the computer and rebooting, running permission verification/repair, etc., usually won't help since these are browser problems.
Few things reveal your intellect and your generosity of spirit—the parallel powers of your heart and mind—better than how you give feedback.~Maria Popova