Glitch with adding custom meta tags!??

Every time I enter a custom meta tag, it sends a ! message saying
“this meta tag has already been added. Please try a different one”
except, I know they have not already been used.
I even tried entering totally unrelated tags to my site, just to test it.
And, every time, that message pops up.
I’ve been trying for days.
In the past, its let me code custom tags. I deleted them all to start fresh, and to see if that was the issue.
(t was not) and now I can’t enter any.
Is any one else having this major isssue!?