Dear Sir,
Manually delete things from Configuration Manager site database is not an officially supported way.
For the issue you got, I suggest that you can try to connect from another provider to see if it makes any difference. check log file smsprov.log and smsadminui.log to see if there is any detailed information.
If it's indeed the SQL DB problem, I recommend opening a support case with Microsoft Customer Support Services as they can work with you to solve this problem.
Best regards
Frank
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