NAS server denies access unless manual

Running Acronis Cyber Protect Home Office Build 39703 (current version). I  am trying to backup a Windows disk over home  network to NAS server on which I am running Ubuntu. When I first create the backup, I can browse to  the disc  just  fine. I create and test the connection just  fine using  the username  and password for the account on the remote  Ubuntu  server,  the connection  tests OK, and  the backup  runs to successful completion. However, on all  subsequent automated backups,  they fail with  the error message "Access is Denied". I am guessing  that for some  reason Acronis  is not caching the  access information when I first create the backup. Has anyone run into this problem  before? Does anyone  know  what to do? The older version  of Acronis used to require me to  edit  the username and  password into  the  URL for  the  server, and  that worked OK, but  that option seems gone  in  the new Acronis.