same here, fixed by going to Xcode -Settings - Accounts and log out my dev account and log it in again

Same issue with the background script loading only once or twice on iOS 17.5 beta(1,2,3), it works reliably on iOS 17.4.1. In my app, which uses only a background script (no content script), I have to force quit Safari and relaunch it to make it work again. I also tried create new Safari extension where I added a webNavigation.onBeforeNavigate listener to the background script. However, this listener triggers only once or twice and requires tapping extension popup to get it working again briefly