Problem solved. Close ticket.
Result of install and run: Blat v3.2.22 (build : Jul 19 2019 23:25:54) 64-bit Windows, Full, Unicode SMTP server set to mail.guardiantm.com on port 465 with user blat@guardiantm.com, retry 3 time(s) Blat v3.2.22 (build : Jul 19 2019 23:25:54) 64-bit Windows, Full, Unicode Error: Wait a bit (possible timeout). Error: Wait a bit (possible timeout). Error: Wait a bit (possible timeout). Error SMTP server error Error: Not a socket. Error: Not a socket.
Old version was Blat v3.2.19 (build : Nov 18 2017 03:14:35) Current version is Blat v3.2.22 (build : Jul 19 2019 23:25:36)
Blat quit working after 6 years on dozens of machines