If an add-on sidebar suddenly says it can't reach your sheet, or you see the message "Authorization is required to perform that action," the most likely cause has nothing to do with your data and nothing to do with the add-on: your browser is signed into more than one Google account.
Why this happens
When a browser is signed into several Google accounts, one of them is the "default" account, the first one you signed in with. Add-on sidebars run in a frame that Google routes to that default account, even when your spreadsheet is open in a different one. The add-on itself never gets a say: Google declines the request before it reaches the add-on, which is why the sidebar can look fine one moment and refuse to work the next.
This is a known Google limitation, open since 2017, and Google's own documentation says signing into multiple accounts isn't supported for add-ons. It affects every add-on from every developer, not just mine.
The fix
- The quick test: open your spreadsheet in an incognito or private window, and sign in with only the account that uses the add-on. If everything works there, this was the cause.
- The lasting fix: give each Google account its own Chrome profile. Each profile keeps one account signed in, the sidebar always finds the right one, and you never see this again.
- The alternative: sign out of the other Google accounts in that browser window, or make the add-on's account the first one you sign into.
In the meantime: the add-on's menu still works even when the sidebar can't connect, because menu commands run on Google's servers as the right account. In Calendar Sync, for example, Extensions → Calendar Sync → Advanced → Sync Now syncs your sheet without the sidebar.
What this is not
It isn't a problem with your spreadsheet, your data hasn't gone anywhere, and nothing needs to be reinstalled. The moment the sidebar runs under the right account, everything is exactly as you left it.
Still stuck?
A less common cousin of this problem: browsers or extensions that block third-party cookies can leave the sidebar hanging the same way, because the sidebar frame needs a google.com cookie to identify you. If you use strict cookie blocking, allow cookies for google.com and docs.google.com and reload.
If a single-account window doesn't fix it, something else is going on and I'd like to know. Write to support@getmarinette.com and tell me which add-on and roughly what time it happened. I can usually see the details on my side within minutes.