It goes both ways — the tool includes BIN to HPT and HPT to BIN conversion, so it's not one-directional.
The likely reason a raw BIN won't load is that the BIN→HPT path expects a BIN that was originally extracted from an HPT by the same tool. HPT files carry segment metadata (addresses, sizes) that gets used to rebuild the HPT wrapper on the way back. A raw BIN pulled straight from a bench read or chip dump doesn't carry that segment layout, so the tool has nothing to reconstruct the HPT structure from.
What vehicle/ECU are you working with, and where did the BIN come from — HPT export, bench read, or something else? That'll confirm whether the BIN→HPT path is the right route for your case or if you need a different approach first.