ERR_TOO_MANY_REDIRECTS after uninstalling plugin

I had tried the Blog Designer plugin, but it wasn’t for me, so I deactivated and uninstalled it. After I removed it I got an alert on my dashboard from the Blog Designer plugin. It wouldn’t go away, and it didn’t have a close button, so I logged off to reset everything and when I logged back in, I received this error on Chrome:

This page isn’t working
greencrest.cc redirected you too many times.
Try clearing your cookies.
ERR_TOO_MANY_REDIRECTS

And my address bar shows:
https://greencrest.cc/wp-admin/admin.php?page=blog-designer-post-and-widget

During all of this my site still ran perfectly, but I could not access the admin panel. So I reinstalled the plugin via FTP and it did not fix the problem. Then I disabled the plugins folder and that didn’t work either. After that I disabled the mu-plugins folder and I got a different error that was from my dashboard, but without the side panel. It said: “Sorry, you are not allowed to access this page.” and it had the same URL as above. So then I re-enabled my plugins folder and everything worked again. But even after removing the plugin entirely, I was still receiving the alert and it still didn’t have a close button to clear it.

After looking around my admin panel for a bit and trying to see if anything stood out as a problem, the alert disappeared on its own. I re-enabled the mu-plugins folder, logged out/in, and then got the same error as above with the same URL. The prompt is no longer visible, but it is still haunting my website somehow and I cannot re-enable my mu-plugins folder without disabling my backend.

Is there anyone who could help me to clear this error so I can fix my mu-plugins folder? Any help is appreciated.