Remote inop is often caused by bad/worn switch contacts. Get a new case for the remote, it comes with a new rubber membrane with the contacts. Like this:
https://www.ebay.com/itm/5-Button-R...3:g:D-cAAOSwqVdapjzv:rk:1:pf:1&frcectupt=true
https://www.ebay.com/itm/5-Button-R...3:g:D-cAAOSwqVdapjzv:rk:1:pf:1&frcectupt=true