When either of the multicall lines on that phone rings, the corresponding multicall key doesn't flash; the prime DN button flashes. This appears to be as designed. Interestingly, for one multicall line, I can press that multicall button when that line rings, and the call is connected just fine. The call display shows the name of the caller. However, on the non-working multicall key, the call display shows "From x277", where 277 is the DN of the multicall line. When I try to press that multicall key, I get a few rapidly blinking dial tones, then a solid dial tone.