how to show safari tabs on other devices

If everything is set up properly, try going to Settings/Your Name/iCloud and slide off Safari syncing. Wait a few minutes and then slide syncing on.

Last resort - have you tried signing out of iCloud and then sign back in?

See iCloud tabs open on other devices

See the webpages open on your other devices in Safari on Mac

https://support.apple.com/guide/safari/see-the-webpages-https://support.apple.com/en-us/HT202530

Related:

Setup iCloud tabs    https://support.apple.com/en-us/HT202530