Heart rate connection faillure

Hi everybody
I’m new at Zwift, the first days everything worked fine but since yesterday (7/8/23)
my heart rate doesn’t go all the way through. It sometimes gives my heart rate for about 2-3sec and then connection failure. I removed the heart rate monitor already and reconnected it and it says connected but No Signal. Can anybody help me solve this?
Kind regards

What heart rate monitor is it, how does it connect, and what’s the rest of your setup

I got a kickr core and a Garmin heart rate sensor.
I know it’s not the battery, because I also rode outside and there the signal never dropped.

Are you using BT or ANT+ to connect to Zwift?
Don’t turn on your Bike Computer ON before everything is connected to Zwift.

With BT there is a problem that you can only use 1x connection with Garmin HR if i remember.

I’m using BT to connect.
Wednesday I thought the problem was fixed. I did a little session and everything worked as it should.
Yesterday I did a workout and the heart rate signal dropped again after a while.
After that workout I did a small lap without my heart rate sensor and somehow for a few seconds it gave a signal and then blank again. Even though I wasn’t wearing a monitor.
I really don’t know what to do to fix this.

I also find it very weird that my heart rate isn’t spiking more. I was doing some intervals and my heart never really went all out.