Step 1 - I verified an account with the CRA using your HIPAA letter.
Step 2 - I sent an offical check from the bank with your HIPAA letter with insert (a) & they signed the green card yesterday.
Step 3 - I got a bill from said OC with the same amount due as my payment dated the same day as they signed for the green card.
Step 4 -

Do I hold off a few days and confirm the check went through the bank? Any suggestions here?

Obviously crossed in the mail,wait until it is deposited, then see if there is any activity on your report.

Use the follow up dispute letter with a copy to the OC if the account hasn't been already deleted.