Chest strap compatibility

Not absolutely sure about the Venu SQ but the Garmin watches I've had only connected to ANT+ HRMs. While ANT+ is a close cousin of BT, it's not the same.

For a while now most garmin wearables support bluetooth sensors as well, and surely the Venu SQ is among them, i.e. in theory it should connect to the Polar H7.

According to the manual, it should be able to connect to ANT+ or Bluetooth devices. And I read reviews where they were able to use an H9, just wondering if someone used it with an H7 too. 

Now I'm unsure if the H7 isn't compatible, or there's something wrong with the watch.

According to polar specs, the H7 should be compatible. Are you sure the strap is ok? Are you wearing it when trying to pair?

I think the strap is fine, it works in Polar Beat and other Tabata timers on my phone. And it also worked with my old (now gone) M400.

And yes, I'm wearing the strap while trying.

I have VenuSq and Polar H7 strap, pairing is unavailable too... :-(

Same here, H7 strap doesn't pair with Venu Sq. Latest firmware on watch and H7 pairs to my 945 forerunner.

Do you have the music version?  The Venu SQ without music only works with ANT+ and the music version works with both ANT+ and bluetooth sensors.  You can see in the specs attached that only the original Venu and the Venu SQ Music support bluetooth sensors.