Mac and iOS not syncing Yahoo Calendar

My husband and I have multiple Apple devices. I have an iPhone and MacBook. He has an iPhone, iPad and a desktop Mac. Our iOS devices do not sync our yahoo calendar with either our MacBook or our desktop Mac. The Yahoo Calendar syncs fine across all iOS devices and our watches.

There are no problems with syncing email across iOS and our MacBook and Mac desktop.

Only the calendar has an issue. This issue started with the recent iOS update.

Note that both non iOS devices are older, yet we never had an issues until the recent iOS updates.

I have tried disabling the calendar on both devices then re-enabling. Ive tried refreshing the calendar. Ive tried deleting the yahoo accounts on both the iOS and Mac accounts, shut down the devices, then reinstall the Yahoo accounts - clicking mail and calendar to share.

I am ready to pull my hair out.

Any ideas as to how to fix this issues?

Thanks