Just ran into this issue today, but only with 1 of my users.
added My: to my configuration.yaml, changed the callback URL in the withings dev portal to Link to OAuth2 Authorize Callback – My Home Assistant and rebooted HA. It’s now showing as connected again even though I didn’t re-authenticate.
I used to have to re-authenticate a few times per week and haven’t had to do so in a good 6 months or so until now. I’m not confident changing the URL will fix this.