Cannot Update Opigno 8.x Module from beta3 to rc

I am new to both Drupal and Opigno. I am trying a test installation of Opigno 2 on a private server (Synology NAS) before I deploy my site. I had difficulties installing Composer under the somewhat quirky Synology OS, but seem to have it operating properly now. My current difficulty is upgrading the installation from the 8.x-1.0-beta3 version which was installed as a tarball to the current 8.x-1.0-rc2 version. When I attempt to do so from within the module update control panel I encounter an AJAX HTTP error; if I try to upload and install the module from my PC I get the error message, "Cannot determine the type of project (Modules were downloaded from https://www.drupal.org/project/opigno_lms/releases/8.x-1.0-rc2; I tried both versions)." Assistance welcomed.