I had a similar problem, my account was missing my last two sailings whilst my wife had been credited ok. Noticed that any marketing emails I received from them had me at gold tier & a different m/ship number.
Emailed & got no reply, waited a couple of months and tried again & got lucky.
Turns out I had two accounts in my name so all sorted.
Keep at it, I must have got someone at the other end who actually bothered to look at the issue.
We're in the UK & mailed mscdirect@msccruises.co.uk, not sure what the equivalent would be in USA.