Are SSL certificates dropping periodically?

Question

IIS

On the instance in IIS, SAN certificates are installed using the letsencrypt SSl console and everything seems to be fine, but from time to time the site stops working. "There is no secure connection
"
I would like to understand what such instability is connected with, and where to dig?
Thank you in advance)

Answer 1

instability is due to the fact that in any certificate there are start and end dates for its validity. letsencrypt has a certificate validity period of 3 months.

Answer 2

Novichok Admin , now there is a quite ordinary certificate for three months (03/23/2018-06/21/2018).
Without any special features.
If something crashes again, you need to look at the reason:
1) in the browser when you open the site - for example - NET::ERR_CERT_DATE_INVALID (expired or not yet);
2) open the certificate in Windows (from chrome: Not protected > Certificate), there we will also see a description of the reason (in Russian).
For examples of what different problem descriptions look like, see here:
https://badssl.com/