..so a week later spacedesk viewer app cannot discover your primary machine anymore?
Are both primary machine and android tablet still connected on the same local area network?
Do you have any third party firewall software installed on either machine?
Do you maybe have VPN (Virtual Private Network) active?
For assistance, please also check Troubleshooting – Network Connection chapter in our user manual https://www.spacedesk.net/user-manual/.