Error: Timeout while resolving TLSA typically indicates a DNS issue with your connection — please check with your internet service provider. The timeout mentioned in the error means that the Flexi application sent a query for a TLSA record but did not receive a response — the TLSA record is either not configured or not available.

Another similar error is UnknownHostException

In the application, this error appears as the message "Unknown data source".

Consult your internet service provider regarding your connection, or consider changing your DNS server as a possible solution. The DNS server in use must support TLSA. Alternatively, you can connect directly via IP address, in which case the TLSA check is bypassed. This solution is only available on a self-hosted server, not in the cloud.

You can also try switching your DNS server to Google's public DNS — see https://www.lupa.cz/clanky/google-nabizi-verejne-dns-pro-rychlejsi-internet/

If changing the DNS server does not resolve the issue, something else may be blocking the communication. This could be caused by a firewall, antivirus software, or similar security tools installed directly on the PC or on the router. In this case, focus on settings such as the Windows Firewall configuration and try adding java.exe as an exception. The TLSA check is performed on every connection attempt.