If RMCTools or RMCLink is having trouble connection to an RMC via USB, here are some possible solutions:
Use Correct RMCTools Version
Some newer RMCs require a minimum RMCTools version. For details, see RMCTools versions and USB drivers.
Repair the RMC200 USB Driver
See Repairing the RMC200 USB driver.
Windows 10/11 HVCI (RMC75E and RMC150E)
RMCTools versions prior to 4.21.0 did not support HVCI on Windows 10 and 11. The preferred solution is to upgrade to a newer RMCTools version. If this is not possible, HVCI can be disabled as described in Enabling the RMC75 / RMC150 USB driver in Windows 10 and 11 with HVCI.
PCs with ARM Processors
See RMCTools on an ARM Processor.