STR Taxes: Rules for expensing taxes/insurance/mortgage interest

[Staton Jobe]

Hey everyone - 

Wanted to confirm something before filing the taxes for my STR, which is located in Virginia.

Am I able to deduct all insurance, taxes, and mortgage interest for the year if my STR was available for rent the entire year but only had renters in it for 150 nights? My CPA is saying I have to pro rate those expenses for the number of nights that it was actually rented out, but I can't find anything online that confirms that. Any 3rd party insights would be helpful before I officially file, as it affects my write offs significantly.

Thank you

Staton