When I go to the store and try to purchase a plan, I click the Checkout button and get an error that says:
You cannot use DNS hosting service for domains with <hosting plan name>.
You are trying to buy a subscription that utilizes a registered elsewhere domain with DNS hosting enabled, while the numdnshosting value in the billable resources of the hosting plan is set to Unlimited (for POA Hosting Plans only).
Such combination triggers the error message above.
The behaviour was classified as the software issue PBAS-29787 and was fixed in OBAS 4.5.4 release.
To resolve the issue, please upgrade to 4.5.4 as described in How to upgrade PBA-S system to the latest available version.