Went from "expert" to ostracized at work when a new prime came in - no idea how this happened. Reddit, judge me then help me!

My first post to the reddit community so I'll see if I can keep the setup to a minimum. Not sure if I posted to the right place, but depending on the answer, it might be.

I'm work with a small business that has been working as a sub-contractor for a government agency on a software development project for the past few years. I am widely regarded (by the client) as an excellent project manager and management consultant, and cultivated an outstanding relationship with the customer, despite the failings of the original prime contractor. My team always ran smoothly and delivered on time.

A few months back, the contract got turned over to another prime, and the company I work for was part of the team that won (I know for fact that the reason they won was because of our company and my personal knowledge). I was retained for that knowledge and my "relationship" (as well as a few of my co-workers), but despite promises of a promotion to a higher visibility position, when it came time for staffing the new program, the new prime demoted me, shrunk my responsibilities, and has kept me out of many important meetings.

As a result they are making decisions without complete information, and despite my significant effort to inform them of the background and my opinion on the matter, they have shut me out (and actually said "we have no interest in doing things the way they were done" - even the things that were done well). I have been informed by the client that they keep telling the prime to involve me, as they are asking questions they should have the answer to, making poor decisions, taking too long to complete activities, and generally have been unimpressive thus far.

I have tried injecting myself into conversations around the office on issues I know the client finds important (when I find out about them), I've picked up tasks that weren't asked for because I saw the need for it. I've tried letting them know I'd love to help them do things in a way the client would be delighted by, that I have a lot of knowledge, and would like to be involved. I've even told them I have nothing to do, and I was told by my boss "Do you think it's my job to tell you what to do?"...

I have two theories for whats going on, but am sure the wisdom here will illuminate possibilities I haven't considered:

1. I've done something personally to offend the team or the prime leadership that have them leaving me out in the cold.

2. They consider my relationship and company a threat, but used us to get the contract and are now pushing us down the ladder (I'm the most senior resource from my company on the project - and the others haven't experienced this).

I used to wake up ready to tackle the day, but these last few months have me dreading even going to work.

On to the ask -

I'd love some insight as to the situation and perhaps what I can do to get back to doing something that has me working more than 5 hours a week (and sitting there for 35).

Thanks guys!