Can't Add Wellmark as an Online Biller?

Is this the Wellmark you're asking about?

Wellmark Blue Cross Blue Shield is a mutual insurance in the United States with more than two million members in Iowa and South Dakota

They don't appear to be listed as Online Biller. I recommend you
logon directly to the biller's website and authorize them to direct debit (aka
PAC Draft, Autopay, APS, etc.) the next and all future payments from your
checking account or a credit card. The biller's computer system will do all the
work for you to make an electronic debit on the due date and you don't have to
worry about being late.

In Quicken just record a scheduled reminder which does not execute as an
online payment into your account register on or before the Due Date and before
you download transactions from the bank or credit card containing the payment
transactions. That will allow Quicken to match your register transaction to the
downloaded data and not cause any further issues.