Advice: employers completely fecked/cancelled my pension contributions

OK, long story shortish.

20/21 asked my payroll and finance team to remove my salary sacrifice of circa £20k per annum as I was getting a mortgage for a house purchase.

Been at the company for 7 years, most senior guys sacrifice above our 5/3 contribution as we are in sales/higher rate tax payers.

Turns out the person removed my salary sacrifice, my contractual pension contribution and my auto enrolment. They also removed me from the Scottish Widows scheme.

Now, my mistake is not checking my payslip more often, I was used to seeing quite chunky deductions, I just assumed (I know my mistake) that my contributions were going in.

When I have now asked to go back to salary sacrifice, this has all been uncovered.

I have also found out I am no longer on the scheme everyone else is on (Scottish Widows) and I was on, that I’m now People’s Pension and my pension rate has changed (no contractual change, letter or comms) confirming this change. Also have told me that I cannot go back on Scottish Widows.

So now my pension is 3/5 not 5/3, no comms, and capped via something called qualitative earnings, with a poorer fund/product and I have had no contributions for several years.

Most frustrating is the company went through administration and is now a new entity so chances of me getting back any monies is not happening.

My frustration is the lack of comms, the downright lies and the lack of transparency.

Any advice?

EDIT: I’m being downvoted and that is absolutely fine. Turns out going back through five years worth of emails is wild.

Eight separate requests for my salary sacrifice to be increased to certain levels over a 24 month period were ignored. Contributions not sent, amounts not lining up and contributions stopping to my SW account in 21, even when I’ve been informed my salary sacrifice is active and at £2000pcm. Contributions are only £700.

I accept it’s on me for not checking or being more diligent, but at no point did I say or ask, REMOVE MY SALARY SACRIFICE. I asked to adjust down.