Hi and welcome to Digi Forum!
Not sure which specific product you are referring to, but TransPort routers should have a PSK max length of 40 chars if SarOS (see: https://www.digi.com/resources/documentation/digidocs/90001019/default.htm#tasks/t_configure_ipsec_tunnels.htm%3FTocPath%3DConfiguring%2520Virtual%2520Private%2520Networking%2520(VPN)%2520%7CConfigure%2520Internet%2520Protocol%2520security%2520(IPsec)%2520%7C_____2 and: https://www.digi.com/resources/documentation/digidocs/90001019/default.htm#tasks/t_configure_user_security_settings.htm%3FTocPath%3DConfiguring%2520security%2520%7CConfigure%2520user%2520security%2520settings%2520%7C_____0).
If they are XOS models, they should have a PSK max length of 255 chars (see here:https://www.digi.com/resources/documentation/digidocs/90002282/default.htm#clipages/r_tlr_cli_config_ipsec.htm?Highlight=psk ).
I hope this helps, if you see any issues, please send an email to firstname.lastname@example.org with all the details of your specific device (IMEI, SN, PN) and description of the issue.
Digi Technical Support Team