Garmin 6 Pro stuck at “Go to mobile app to add device”. Won’t respond at all, won’t add to phone.

A new watch in initial setup? or after a reset?

After reset

As it’s a Reset, try going into Phone Bluetooth and remove it there and in app Remove Device. 
That should remove old connections. Now in App try to Add Device making sure you have your 66 Pro with Pair Phone selected.

Press and hold top left until shutdown then restart and try again.

May I ask how did you resolve this? I’m having the same problem.. 

SergioReal said:

May I ask how did you resolve this? I’m having the same problem.. 

The hints posted in the thread did not help? In that case I recommend reaching out to the Support.

Maybe not the same issue, but I had a similar problem with a 6X. Could not pair, tried reset, reinstall GCM etc many times. But when wifi was set off on the phone it worked at once.

So pairing worked with the cellular data connection only.

There is a beta version on my 6X, so I reported it as a bug in the beta space, however it can be a problem with GCM.

I don't think the issue was with the phone, but can't exclude the possility.

Data said:

I don't think the issue was with the phone, but can't exclude the possility.

If disabling Wi-Fi on the phone helped, then the phone is the main suspect. And indeed, interference between Bluetooth and Wi-Fi (both using the 2.4 GHz band) are quite common. Very often we hear about this kind of problems especially at certain Samsung models, although other brands may be also concerned.

Some tips that may help are for example here:

Wifi connectivity issue when any bluetooth devices... - Samsung Members

Using the 5 GHz band for Wi-Fi (if you have a 5 GHz wi-fi access point) should also help in such case.

The problem is also addressed in the Sync / Connection Troubleshooting Guide

Google finds many more results on this subject: samsung phone wifi interfering with bluetooth - Google Search

Thanks for those references. It was a new experience for me, I used the same Samsung phone for some 10 years with Fenix models old and new, without issues like this. Maybe the recently purchased mobile dataplan changed something. (BTW I am aware using old tech can have security risks).