Customers often ask this question. See below.
A gray panel means that the system is not getting data for that TS4. There can be many causes for this. The most common cause is poor communication. Poor communication can also have many causes, but the most common cause is poor TAP placement. If the TAP is too far away or there are obstructions preventing good data transmission, this can be the result. This cause is particularly likely if the problem is intermittent (comes and goes). If the panel is gray and stays gray all the time, then it could mean the TS4 is damaged and not operating properly.