Hi, welcome to justanswer.com! My name is Mike.I am going over your question and I will be with you shortly.
You have to erase the drive or get a new one it is full.
I can help you by remote
Ok turn off Time Machine then open the Disk Utility select the drive and erase it name it something different then add it back to Time Machine and turn it back on.
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Did you erase the drive?
Do you still need help? You never replied.