Leaving comments on my blog

It may be a simple problem, but I give up searching through all the bits here as I cannot find the solution.

Only a few people can post on my blog, the majority cannot.

This is the error “Sorry, you must be logged in to post a comment.”

Below is what I’ve selected in Discussion Options:

Usual settings for an article:
YES – Attempt to notify any Weblogs linked to from the article (slows down posting.)
YES – Allow link notifications from other Weblogs (pingbacks and trackbacks.)
YES – Allow people to post comments on the article

E-mail me whenever:
YES – Anyone posts a comment
YES – A comment is held for moderation

Before a comment appears:
YES – An administrator must approve the comment (regardless of any matches below)
YES – Comment author must fill out name and e-mail
NO – Comment author must have a previously approved comment

And as advised, I do not have anything blacklisted.

This is my blog:
https://www.designers-who-blog.com/

I’m constantly getting emails from those would would love to post but cannot.
Suggestions?