5304 can't pick up call on multicall line

[handwritten]

This is a weird one.  I have a 5304 that has two multicall lines as well as the prime DN.  When I call the multicall number, other phones can pick it up, but not this one.  When I try to pick up the call, I hear a dial tone!  There's no DND set on the phone, and nothing different about this configuration.  What am I missing?

[acejavelin]

When you answer the call, are you pushing the line key that is ringing? You might not have Ringing Line Preference in the class of service.

[handwritten]

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.

[acejavelin]

Only the first 2 keys can (should) have line (DN) appearances...

[handwritten]

Right. But multicall lines appear in many places in our organization on the other keys, with no apparent problems.

[johnp]

5304 has only 2 keys that light prime and 2. I have never tried adding a third or using anything above 2 for a multicall