When you use the task notification in the BLE task to finally start the measurement loop it must be outside the loop, right ? Otherwise it’s waiting again on the next loop iteration and waits forever.
That would be a simple programming bug you could easy track and find out with a debugger just stepping through the (measurement loop) code. The same applies to the verification if the dk_task works as desired. Set a breakpoint at the next line after waiting for the task notification, step through the code to see what’s going on. Also the variables can be inspected or watched.
I’m unsure - do you know what a debugger is ? If not you really should find out. You’ll need it 