Where do I go to enter the loss of rental income for a part time home?

Loss of rental income is not reported on a tax return.

Income that was not received can never be entered as an expense or deduction on a tax return.

From a tax perspective, there's no such thing as "loss of rental income".  You only report rental income you actually receive. If you were not paid rent for a period of time for any reason, then you don't have that income to report anywhere on a tax return.

Take note that with an insurance payout on a claim, that payout will usually include an amount for "loss of rent". That specified amount "is" included in the rental income and gets reported as such.