Time Machine couldn’t complete the backup to “Time Machine”

I am having problems backing up to Time Machine. I have not been able to backup since August. I get the following:

I have an internal 4TB SSD with 204.6GB free. The external drive is a 4TB HDD.

From what it says, TM deletes old backups and replaces it with new backups. If that's so why can't it do that? Its confusing since there is 200GB free space it should be able to make a backup with no error, shouldn't?

This has been the case for a long while now and I can only get it to make a backup when I erase the TM drive and start over.