Not a bug with e621.net itself but the tagme.dev:

If a user does not have any tags listed in their blacklist (in this case me, because I don't give a shit about anything enough to blacklist), TagMe will give the following message in the F12 Console menu:

❌ Uncaught (in promise) TypeError: Cannot read properties of null (reading 'split')
- at reloadBlacklist (script.js?2104151843:1634:63)
- at async BlacklistHandler.build (script.js?2104151843:1605:13)
- at async run (script.js?2104151843:1516:5)

Take me with a grain of salt (because my dumbass flunked a Python course): The way I understand it, a blacklist without anything to read will leave TagMe unable to look through any posts to compare its search against, and consequently the /resolve/ page will have a constant grey loading icon with "#0 | Loading | history" underneath.

Adding at least one of any tag (such as this_blacklist_empty_yeet) will fix TagMe into parsing correctly.

This section is for reports about bugs on the site, I would post this on the github issues tracker (https://github.com/bitWolfy/tagme/issues), but the last code update was 2 years ago.