DNS TXT records input field max length value is too short.
Ex. When you add Dkim record to DNS TXT record, definied maxlength="255" is too short, so you can save dkim ecord in your DNS settings.
Above Dkim recors value about 411 chars.
v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAsGaMgRePE1NRR+SeQdAFOxx1TY5rDTJQeXCclsQPk2r1TrYLXzrxrkpP5yZkcGtaADgSolQCBmbg2+aafZ/Z85y056jwD3tA37NgvNGUmtrj1oQ+ksXMy4OcE567C1F+UQtVNEVDM+KdSHhxaDzdWYVMidbs3DIEqWJ0zvmvbzUFOKI1pPeOmytuNLYj6mNRt3q9qC7fdXxkfXlV89KVORBdrDunujBpoSr3Wj3lJbINAHOhO7uaEQRoJWI/2Wh23Jza5xvACJCb31+P1J0r2D95pWkOtGw3Ouh4uGOdO31KdzNUTFcjHA7nLcuRm8AIqWWAoysoY7xiYM3u3TwIDAQAB;
I hope you help, and you correct tempalte files and database char table modifications.