404 after new post

I’m getting a 404 page after attempting new posts. The 404 says:

I’m pasting from text from NoteTab.
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Done all the normal things, i.e.
– turn off all plugins,
– go to default theme, etc.
– Recopied all files and folders from a fresh unziped file of 2.91
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-The 404 says”The server encountered an internal error or misconfiguration and was unable to complete your request.”

“Please contact the server administrator, [email protected] and inform them of the time the error occurred, and anything you might have done that may have caused the error.”

“More information about this error may be available in the server error log.”

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
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Ive phpadmined and repaired all the tables

Any help?