Re: With new Let's Encrypt certificate, "Check For Update" failed.
I have sent you an email with a debug version of WinSCP to the address you have used to register on this forum.
Before posting, please read how to report bug or request support effectively.
Bug reports without an attached log file are usually useless.
2016-05-30 15:01:29.965 Doing SSL negotiation.
. 2016-05-30 15:01:30.169 ssl: Verify callback @ 1 => 20
. 2016-05-30 15:01:30.180 ssl: Verify failures |= 8 => 8
. 2016-05-30 15:01:30.214 Chain depth: 2
. 2016-05-30 15:01:30.225 ssl: Match common name 'winscp.net' against ''
. 2016-05-30 15:01:30.235 ssl: Match common name '<www.>winscp.net' against ''
. 2016-05-30 15:01:30.247 Identity match for '': [b]bad[/b]
. 2016-05-30 15:01:30.259 ssl: Match common name 'Let's Encrypt Authority X3' against ''
. 2016-05-30 15:01:30.269 Identity match for '': [b]bad[/b]
. 2016-05-30 15:01:30.280 ssl: Match common name 'winscp.net' against 'winscp.net'
. 2016-05-30 15:01:30.293 Identity match for 'winscp.net': [u]good[/u]
. 2016-05-30 15:01:30.304 Verifying certificate for "winscp.net" with fingerprint cf:11:88:6b:8e:27:f6:09:ea:01:ab:c5:71:df:cc:03:0a:f7:f1:13 and 08 failures
. 2016-05-30 15:01:30.316 Certificate for "winscp.net" matches cached fingerprint and failures
. 2016-05-30 15:01:30.328 Using TLSv1.2, cipher TLSv1/SSLv3: ECDHE-RSA-AES256-GCM-SHA384, 2048 bit RSA
. 2016-05-30 15:01:30.340 Request sent; retry is 0.
https://winscp.net/
, as if it were a WebDAV server and attach a Debug-2 level session log file.