Here is the link to the company website page for my new used amp. The quick start guide and manual can be downloaded from here: https://shop.fender.com/en-US/guitar-amplifiers/contemporary-digital/mustang-i-v.2/2300100000.html
Googling "fender mustang 1 20W amp" gets that page, plus ebay, Amazon, and guitar center pages, and forum threads about how to reset it.
