Help Needed: Issues Accessing File Shares and RDP on New Windows 11 Workstations

I'm having a frustrating time with two brand new HP Elite 805 Mini workstations that were set up with Windows 11 Pro. Our company utilizes QuickBooks in multi-user mode, and both machines need to access the same company file from the primary workstation. However, the second workstation is unable to log in and access the shared folders; I'm greeted with requests for a username and password, resulting in event ID 4625 with status 0x0c00000D each time.

Here's what I've already tried: setting up a local user for file access (using the hostnameusername format), ensuring that user permissions are configured correctly, enabling network discovery, adjusting firewall settings, turning off password-protected sharing, verifying SIDs, and even installing SMB 1.0/CIFS as a workaround. I also looked into making RDP connections, but I faced the same event ID issue. I've ruled out on-prem AD and Azure AD being factors, as our network is a flat setup with all devices in one subnet. I suspect this could be related to a recent Windows update (KB5065426) that has caused similar issues for others. Any advice would be greatly appreciated!