Hi Scottle,
I'm Cherrelyn, I'm here to help and I understand how frustrating it is when you can’t connect between your own PCs despite doing everything right. Please try to use the exact username and password of the target PC check from Control Panel > User Accounts. If there’s no password on the account, try setting a temporary one and Windows often blocks connections to accounts with blank passwords. Ensure both PCs are in the same workgroup Control Panel > System > About. Open Credential Manager on the connecting PC search in Start, and add a Windows credential manually using the IP address and account info of the target PC.
Let me know how it goes and I'm here to guide you for further assistance.
Warm regards,
Cherrelyn