It is unclear what happened and what you expected to happen.
1) You bought it for $360k and sold for $405k for a "gain" of $45k.
2) I don't know where the $100k you are talking about fits in.
3) You had 14 years of depreciation which I don't see in this calculation.
4) Any improvements made in 2020 would be added to the basis and will reduce your gain.
The main issue is the depreciation. Even if you never took it, you still have to recapture (pay taxes on) it.
