Since Friday June 16 no storage of HR and BB with my Swim in the Connect app. How come? Please help.

Try a restart of both watch and phone. 

Thanks for your response. But of course, done that several times. No succes.  

Remove the watch from Garmin Connect, sign out, then sign in, and add the watch back again. See the next day whether it helped.

Thanks Trux, I just did that (again). Let’s see what tomorrow will bring.

The app doesn't store anything. Everything is stored at Garmin's servers. There is no limit to how much data you can store.

Do you see your HR and BB on the watch?

Sync with Garmin Express and see if that helps.

There is no limit; there are countless of users with more than a decade of data. Either you have a hardware problem (but the watch would not show any HR either), or a storage failure on the watch, not keeping the monitoring data, or a problem with a phantom account, or a secondary device (another phone / tablet) messing up the syncing. Do a soft-reset of the watch (on most watches holding the Light button for ~20s till it shuts down), and then follow carefully the instruction in the hint #4 of the Troubleshooting guide for (some) data missing after syncing 

Also make sure there is no other device than you primary phone, connected to the watch.

You can check also the other hints in that guide, though my first suspicion in your case would be the #4.