How to make nginx ask for a certificate password?

Question

Nginx

I set up a bunch of nginx + apach on Debian, connected https on nginx and installed certificates (with a password)
When I restarted nginx from the console, it rebooted and asked for a certificate password, after entering everything started fine.
All this worked for several years, but today I needed to reboot the system, after that nginx refuses to start (and does not ask for a password for the certificate), in the logs it swears at the certificate, although the test passes (during the test, the password is requested). Tell me what could be the problem with

nginx logs

2018/12/10 23:24:18 [emerg] 3486#0: SSL_CTX_use_PrivateKey_file("/usr/local/etc/ssl/site.ru/www.site.ru.key") failed (SSL: error:0906406D:PEM routines:PEM_def_callback:problems getting password error:0907B068:PEM routines:PEM_READ_BIO_PRIVATEKEY:bad password read error:140B0009:SSL routines:SSL_CTX_use_PrivateKey_file:PEM lib)

Answer 1

why? what task is solved by the password?