It is possible your locals are on the 77 satellite still, if this is the case the new Eastern Arc LNB needed for the Hopper 3 won't pick up the 77 satellite.
Yes, the H3 is available on Eastern Arc. It does depend on your account though as we often have the wrong orbital tags on the account. Please send me a PM with your phone number and 4 digit PIN and I can take a look
Before I shoot myself in the foot on this upgrade, what is the maximum distance between the dish and the hybrid solo node? My dish is at least 150" from the receiver.
Funny because it's totally wrong and there are thousands of people using the H3 on the Eastern Arc. Sad because you got that bad info from an official DISH rep who apparently needs more training.