Samsung Galaxy S — Calendar Apps are not syncing to my Galaxy s7

Hi, I'm glad to have found this forum and hopefully get some suggestions on how to solve my problem.
I have the Galaxy s7 phone and the Galaxy Tab A tablet. Both have v.7.0 on it.
I also have DigiCal, Google cal. and Samsung default calendars installed on both devices.
When I enter an event on the phone, it shows up on all 3 calendars on the tablet.
When I enter an event on the tablet, it does not show up on any calendar app on my phone.
It seems that my phone is "sending but not receiving"
I have spent a lot of time trying to solve this problem and looked through all of the settings I can think of. It seems that somewhere I'm missing something but just can't find it.
If anybody has any suggestions, I would appreciate it very much. Thank you in advance.

Thank you so much for your help. I have tried your suggestions. Calendars from Tab A to Gs7 still are not working at this time.
However, the "Color Note" and "Keep" apps are now syncing. This was one of my other problems I have not been able to fix for some time.
So, I'm on the right track. Will have to work with the calendar apps again....
Thank you so much for your help.!!