Very confusing letter re ESA

Hi, I applied for New Style ESA on 4/4/19, completing the form at the Job Centre and assisted by the Personal Advisor. I was called23/5 for assessment on 14/6 in York, which I attended thanks to full support of a friend (a trip which took 5 hours). On 29/6, I received letter stating cannot get ESA because I have not paid or been credited with enough NIC using tax yrs ending 5/4/17 & 5/4/18. (t/c to NIC contributions verbally confirms that I have and are sending me a statement)The letter then states they may credit me with NIC while claiming ESA.
To continue to receive ESA I may need to attend work focus interview (have already done that) and may need to attend Work capability Assessment - that was done on 14/6.
Mandatory recon. t/c on hold for 45mins, got through to Adam, who was unable to see the letter, could not tell me where the NIC information had come from, and could not see that I'd been called for and attended assessment. Do you think I've got grounds for complaint as well as Mandatory recon? Am so stressed D&V.

Thanks, I will be getting the proof from NICs - but I'm concerned that they don't know about the assessment (and so why have I had the letter ?) Also the letter itself is very confusing none of my family or friends can work it out. I'm struggling so badly with multiple conditions, one being diabetes and have very high blood sugar, made much worse today by D&V brought on by stress and worry.

Hmm, well I would be very keen to know why I was called for an assessment before they even knew if I qualified.
Thanks anyway, I'll try and keep going!