I've been having the same problem on and off. I can get the balance on my Nationwide CC account but individual transactions ceased on 20th Jan 2020 and nothing since despite successfully reconnecting numerous times.  It happened twice last year when it stopped working for 6 weeks - only to update without warning without any apparent reason/action on my part - updating the missing period.

Now getting so frustrated as we have to submit VAT digitally and I'm just a few weeks away from my next one to be submitted without the complete data !

Also noticed a while back that often transactions are missing from the date at which the CC becomes payable date to the date which a new statement is generated - so watch that one folks !!!

Nationwide tell me its Quickbooks and Quickbooks tell me its Nationwide !!!! Pretty sure I'll be switching to Sage at the end of the financial year this is too much like hard work and Quickbooks offer no compensation for the costs I've incurred getting my accountant to help me - and still have the cheek to charge the full subscription ! So FRUSTRATED I COULD SCREAM !!