If it makes it into test mode on start up, something in the boot loader stage is hanging up. You might try a sysex firmware reload but if you haven’t done a recent backup I would only reload firmware, I would not factory reset.
If you can’t make it into test mode, the machine might be bricked, but I don’t want to jinx you. You need to contact support because it will probably save you some time, even if they’re slow to respond.
I had this too after a couple months of owning the original Digitone. There was no way to fix it, support had me mail it back to them. Turnaround was a month or so.
Elektron support offered spare main board for cheap but I wanted to repair and save e-waste.
I inspected the electronics, fortunately was repairable. One of the big BGA chip needed a resoldering.