TRYING TO PAY MY DOCTOR: WHERE'S MY CLIENT ID?

So, I'm trying to pay my medical bill, and it says I need a client ID. Here's the catch: I can't find it anywhere! Searched everywhere online. Did my doctor's office send it to me? Do they have a different website? Any ideas on website how to this client ID would be greatly appreciated. Logging in to Veradigm Pay My Doctor with Payment Issues