Hi,
in Your page
https://wiki.postgresql.org/wiki/Community_Guide_to_PostgreSQL_GUI_Tools
SQuirrel is listed as no longher supported:
SQuirrel: website 404. http://squirrel-sql.sourceforge.net/
But SQuirrel is still supported, works on PostgreSQL and the
http://squirrel-sql.sourceforge.net/ is working...
Maybe the error was due to an external problem
Best Regards,
meo bogliolo