Hi @estley and welcome here in forum!
Try to delete BigBear Store:
Add store again:
More Apps button. Paste this:
https://github.com/bigbeartechworld/big-bear-casaos/archive/refs/heads/master.zip
More button is link here:
https://awesome.casaos.io/content/3rd-party-app-stores/list.html#_4-casaos-edge-appstore
if does not work (You mentioned You uninstall it many times), try to restart casaOS service inestead of reboot whole Host.
Servicies must be started in specific order!
casaos-gateway.service
casaos-message-bus.service
casaos-user-service.service
casaos-local-storage.service
casaos-app-management.service
casaos.service