DOCTOR BILLING DILEMMA: NO CLIENT NUMBER

Ugh, I have to to pay my doctor's bill but their system is giving me a fit! It keeps asking for a client ID and I have no idea where to find it. Did anyone else run into this? I've checked my email, statements, and even searched through old paperwork, but nothing! Is there a secret location for these IDs or am I just missing something obvious? Ple

Has anyone else been having issues logging into PayMyDoctor/the PayMyDoctor app/their PayMyDoctor account? I've been trying to log in/trying to access my account/having trouble getting in for the past couple of hours/few minutes/an eternity and it just keeps saying that there's a problem/giving me an error message/telling me to check my connection