Sounds like a 'standard' pairing problem. These are usually solved with some patience. Check to make sure the switch is not available to SmartThings. If ST sees it then it hasn't been excluded from ST. Then it can be included to HE. I don't know what chicken dance is required to get your switch into pairing mode but it's probably in the manual or better yet search the forum for you model number or brand.
I am also trying to "find" and include the same LInear wz15z switch and Hubitat will not discover it. Ive tried to exclude and it doesnt find it. I try to include and it still doesn't find it. Ive pout the Hubitat within inches and still nothing. Anyone have an idea ?