Other software that uses standard OBDII protocol usually work with these adapters, so people usually don't understand the problem. FORScan uses service level protocols and requires adapters that are fully compatible with original ELM327. 'Bad' clones are not fully compatible with original ELM327 and will not work with FORScan. In past few years 80% of them are 'bad' clones, and unfortunately this ratio grows.
Important note: almost all of adapters sold under 'ELM327' label are 'clones' (use not original ELM327 chip).
