integration with mail chimp stopped working

please help. i am not techie but just need my one newsletter form to link to my one mail chimp list but although i managed this for years, it has stopped working and i am paying for adverts to send leads into the void.

i have disconnected and reconnected. it says connected at both ends but is not populating my test email.

i have tried creating a new empty audience in mail chimp and that worked for a while.

atm i am having to take emails across manually.

please advise...how hard can this be?!  [P.S. I am asking you guys because MC is absolutely awful with customer support and I am loathe to employ another Upworker in far flung lands just do this one task]

thank you