I got my LimeSDR mini v2 a few months ago and shortly after getting it the led is solid and no longer enumerates as a USB device. I did update the firmware.
I have tried multiple systems and different USB ports as well.
I tried contacting crowd supply for an RMA but they told me to go here and I just haven’t had time to get around to it.
It sounds like you may have managed to brick it and if you cannot reprogram via JTAG, RMA is likely the only option. Please consider this post as RMA authorisation.