Unless the console is out of battery, it will never lose the ability to enter RCM. The proper procedure is to ensure you are actually entering RCM which includes making sure that you are doing it properly on your console as well as double checking that your computer or other device is checking that it is in RCM. Entering RCM is a manual process without AutoRCM therefore it is subject to user error so whatever you are using to enter RCM can simply not work from time to time. As for your computer or other device, they too sometimes do not recognize a console being in RCM which is harder to fix as there the cause for this has not been identified. Restarting your computer/device, trying out other ports/cables, or using a different device entirely are the only suggestions I can think of.