Calendar not synching

Hi, I use my Disroot calendar on Thunderbird on my laptop - no problem - and on my android phone using Etar and syncing with Dav. Sometime in the last week or so, the phone and laptop stopped synching with each other. I tried opening the calendar on Disroot, and it syncs with the laptop, not the phone. Any suggestions? Thanks.

PS I’m one of the Luddites, no jargon please…

What android version are you using?

6.0.1

I don’t use google on my phone, so I’m not sure if I can update it.