Is there a difference between unaccessible and inaccessible

Though listed in some dictionaries, unaccessible appears to be just an uncommon variant of inaccessible as suggested by Google Books .

Note that:

Un- is the most prolific of English prefixes, freely and widely used in Old English, where it forms more than 1,000 compounds. It underwent a mass extinction in early Middle English, but emerged with renewed vigor 16c. to form compounds with native and imported words. It disputes with Latin-derived cognate in- the right to form the negation of certain words (indigestable/undigestable, etc.), and though both might be deployed in cooperation to indicate shades of meaning (unfamous/infamous), typically they are not.

(Etymonline)