Problem of data base syncing

I am a french student using Anki dayly, however since some days I don’t arrive to synchronise my cards from my computer app and I have always have this error message when I push the button “sync” : “Please use the Check Database function, then sync. again. If problem persist please force a full sync in the preferences screen”.
Of course I check nearly 100 times the check database on my phone app, my computer app, but I always have this message and it doesn’t synchronise my cards anyway with web. I looked for answer on web but I’ve found nothing.

Can you help me to resolve this problem I don’t know what to do. Thank you.

Did you force a full sync in the preferences, upload on your device, and then download on your other device(s)?