HOA's Management Company seeking "rental fee"

As this site hosts so many great minds, I'm back for some advice:

We own a great townhome in MN.

We've had a terrific family in the home for nearly 4 years (and another family that lived there for 4 year before as well).

The HOA's Rules & Regulations specify that in the event of a rental, the owners will pay the Management Company a specific cost for a background and credit check. We abide by that rule and take great pride in following the HOA's Rules & Regulations.

The HOA recently (a little over a year ago) changed the management company that oversees the property.

We just received an email from the management company, asking if our home was a rental (it's in their records along with the current lease), and if so, that we need to pay a $200 fee annually to them for having a rental.

Going over the Rules & Regulations, there is absolutely no word on such a fee. 

We haven't responded to their message and I'm wondering if I can refute it in any way. 

Beyond the high amount they charge for their credit and background check, this $200 a year seems like a money grab.

Would appreciate some insight to see whether I have an argument here or have no choice but to pay them.