Because it is not rented (and was vacant for 1/ 1/2 year); you cannot claim expenses incurred for repairs or taxes. You can only claim amounts to your ACB to reduce your capital gains.

Can you claim the months your basement suite goes un-rented (for mortgage interest, insurance, and property taxes?  Our suite was rented 6/12 months in 2018 (due to slow market)

@kerbare10  - only if you have made a reasonable attempt to rent and can prove that you have, otherwise no.