Wow! This is still not resolved!
To explain - what @sdt_kparent and @Chris-B are saying - if you have access to the deactivating user’s email used for Hubspot, you can change the password on the email account and restrict the user from accessing it, and then reset the password on HS so they will not be able to get in again. However, as @KevinWebb22 is saying, a user can still get in with the old password. Unless he is mistaken and the user just reset the password again, then the first solution is not good. Can you clarify that @KevinWebb22 ?