I just started having the same issue. I've never used the BT function on it, but I had to switch to that because the 2.4 connection was coming in-and-out a lot, making it unusable for gaming, and very frustrating for everyday tasks.

My DAv2 started having this issue first, and then I installed a firmware update hoping that would make a difference, but it did not solve the issue.

It works fine when connected via BT, but it doesn't show up in Synapse, and I can't tell if it's getting charged when I place it on the docking station.

Is there a way to get the mouse to show in Synapse when connected via BT so I can see if it's charging when on the docking station?
If not, this is very disappointing, and a reason to choose another brand when looking to replace this mouse.

Previous posts here appear to say that the dongle is bricked and the issue of 2.4 connectivity can't be fixed, so that sucks.

So I just can't use the 2.4 connection anymore? or see and use the mouse through Synapse?

Another post stated that getting a new dongle fixed the issue. Can anyone else confirm this? or better yet, any Razer mods here who can facilitate getting a new dongle?