Seller-fulfilled listings removed due to VTR below 95% - Help please

Evening
I received the following message below today

We have removed your seller-fulfilled listings in the following categories: Home,Kitchen,ofice products Why did this happen? We have taken this measure because your Valid Tracking Rate is below the goal of 95% in these categories.

I thought this was all sorted a few months ago as I post with jut 1st Class and 2nd Class stamps and 1st and 2nd Class Large letter stamps. My VTR went to N/A so thought all was ok until this.

As I am now being asked to report an action plan to them, I am unsure of what to do. Any help or advise would be grateful.

Thank you