For anyone reading this thread and wants to avoid the nightmare Shopify caused me - if you get this error:
There is a problem with your UPS account, please contact shipping-ups@shopify
All you do is find an old label and the first 6 (six) digits after the 1Z is your account number - 1Zxxxxxx09873 - call UPS and give them your account number and they will most likely tell you there is a small outstanding balance (mine was $30) - you pay them with a credit card and they turn it back on immediately! Shopify couldn't figure this out at all - 5 days of responses telling me to wait................grrrrr...... I hope this can help someone not have to deal with what I did!