Trackpad won't stay on

Hello,

I haven't used my trackpad for a bit now, but I am recently trying to use it again. However I am not able to connect to to my iMac. It had been paired before, but now when I hold the power button on the trackpad it simply blinks once and turns off. It doesn't continually blink as if its discoverable mode. no matter what I do with the power button: hold >10s, hold ~5s, or tap the response is always the same. I turned off my bluetooth, unpaired it, turned back on bluetooth and tried to pair but it wouldn't show up. Of course I replaced the batteries first.

Any ideas how to fix it?

Thank for your help