I’m having a similar issue (with Bubble-Card), and did have same issue with Tabbed-Card last week.
I am also searching for a solution.
I did get the card to appear by going to the Resources Tab, opening the specific resource, and clicking the UPDATE button (without changing any resource information). When returning to the dashboard, it appears again. However, as soon as the page is reloaded it comes back with Custom Element Doesn’t Exist.
If you’re up for trying it, let me know if you experience the same brief success. Perhaps we have a common config issue
I tried some experiments but nothing worked. I ended by making my own tabbed content with CSS. Maybe an integration who have conflict with those one but i don’t have time to try and die for now