Do all 2 unit condo master policies require an insurer

[Jake Durell]

My wife and I own one unit of a 2 unit building which we are living in. For whatever reason, we have an HOA for the building. The other owner own rents the upstairs.

When I started inquiring about coverage for STR in my unit for part of each year (~3-6 mos), the commercial agent claimed that the HOA master policy we had didn't cover the upstairs owner's rental. I'm looking at the insurance binder now for the "Business Owner's Policy" for the HOA, and I see the words "landlord" and "tenant" all over (e.g. "Covered Property, as used in this policy, means [...] Your personal property in apartments or rooms furnished by you as landlord"). It's possible that before my time running the HOA, the original policy was purchased when there was no tenant, but neither I nor the prior HOA head was ever asked about rentals over the past 7 or so renewals. 

Now the agent is telling me that we have a gap in coverage now, and no insurer will insure us unless we have a property manager. They have yet to give me a hard and fast requirement of what qualifies as property manager. E.g. can I or the other owner be property manager? They said something to the effect of "it would be good if it were a professional company that is insured" but did not go so far to say that insurance was a requirement. 

This seems excessive for a 2 unit building where the owners are around and care about the property. Are there insurers that will let me focus money and effort caring for the property rather than retaining some token property manager that has little to no function other than what is needed to help us check a box?