Yes, I was in the same boat. No resolution from the afore-mentioned troubleshooting but I did reach out and the problem has been resolved. I've been using Quickbooks for training purposes and during a 1hr+ phone call with the customer care team, I discovered that I had a filter turned on. Clicked the "clear filter" link and all my customers reappeared although I'm not sure how I applied a filter to begin with. At least I know what to watch out for in the future!