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 related 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 settings as a possible solution. The DNS server in use must support TLSA. Alternatively, it is possible to connect directly via an IP address, in which case the TLSA check is bypassed. This solution is only applicable on a self-hosted server and is not available 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. A firewall, antivirus program, or similar security software installed directly on the PC or router may be interfering. 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.