ERROR in initial install/setup

hello. my search for a “simple” PWA plugin lead me to yours. so i went ahead & installed it in a staging environment that my server/host provides (SiteGround). so my problems might be due to that (not sure). the staged site is password protected too.

upon activation i made my way to the Settings > PWA page, and at the top it says:

ERROR: PWA – simple way to Progressive Web App

The “manifest.json” file is no reachable.
Please change your permalinks settings or server rewrite rules.

clicking on the “manifest.json” link opens that file. i can see the json code, so i’m not sure why it says it’s not reachable.

so then i clicked on the “change your permalinks” link and i “flushed” them. note: my permalink structure is using the “Custom Structure” option with “/%category%/%postname%/” in that form field. would that be causing the problem? i don’t really want to change that if i don’t have to.

now, if i make a minor change (like to the short name) and click the “Save Changes” button, that error message goes away & i get the “Settings saved” confirmation.

BUT, if i go away then come back or reload the page, then that same error message re-appears. AND not only on the PWA settings page, but on ALL admin pages.

so what am i missing? is it just because it’s on a staged & password protected site? any ideas?

thanks.