Good day, @HFields.
Let me chime in on this conversation and clarify things with regard to managing company files in QuickBooks Desktop (QBDT).
First off, yes, I agree with @Fiat Lux - ASIA that the ability to open two company files at the same time is only applicable when you're using QuickBooks Accountant or Desktop Enterprise.
Pertaining to your second question, yes, we can have three company files under one subscription. However, opening these at the same time is unavailable. You might want to look for any supported third-party apps that can make this possible. Feel free to utilize this link to look for one: Apps help QuickBooks run better.
Additionally, I've included an article that you may use for future use to learn how to fix company file issues in QBDT: Fix company file and network issues with QuickBooks File Doctor.
Keep your post coming if you've got additional questions about managing your QBDT account and company files. I'll be right here to assist you further. Take care.
