Archicad must be able to communicate with BIMcloud / BIMcloud Basic to provide Teamwork. To verify this, run the Network Diagnostic Tool from the Open / Join dialog or the Teamwork Palette. Verify whether all necessary ports are open and the server machine is available from the client machine.
Whenever possible, use wired connection to the network. Try turning off the wireless connection to make sure you can access the BIMcloud / BIMcloud Basic's computer over the network.
3rd party applications are blocking the communication on the server side
Antiviruses, firewalls, backup or any other monitoring applications (e.g. Windows Search, macOS Spotlight) tend to scan all files in real time, which can cause huge performance issues on the server side. Turn off file indexing and add the Projects and Attachments folders to the exception list in your antivirus / firewall settings.
3rd party applications are blocking the communication on the client side
Similar to the server side, monitoring apps can interrupt the communication between Archicad and BIMcloud / BIMcloud Basic. In the settings of the above-listed applications, add Archicad and its folders to the exception list. Make sure to schedule 3rd party backups to run outside of working hours.
Project needs to be re-shared
If you have a scheduled snapshot, restore the project by using Rollback BIMProject or Library Snapshots. Else, save a local copy (PLN) from the project and open the PLN with the Open & Repair function. Save the PLN again and re-share this file to the BIMcloud / BIMcloud Basic.
If you still experience the above issue, please contact your GRAPHISOFT support representative. For the investigation Archicad FastLogger files and BIMcloud log files might be necessary.