nginx warning after installing Plesk update 61: [warn] the “listen … http2” directive is deprecated

Symptoms

1. Plesk update 61 has been recently installed on Plesk server with previously enabled HTTP/2

2. Command # nginx -t or cron tasks show error:

New configuration files for the Apache web server were not created due to the errors in configuration templates: nginx: [warn] the "listen ... http2" directive is deprecated, use the "http2" directive instead in /etc/nginx/plesk.conf.d/webmails/example.com_webmail.conf

Cause

Nginx directives for HTTP2 were updated by package vendor. Web server configuration was not regenerated during the update installation to avoid unplanned websites downtime. 

Resolution

1. Applying the solution on a server with thousands domains can increase temporary sites downtime. In that case, apply the solution during server maintenance hours.
2. Log in to Plesk via SSH
3. Trigger nginx configuration files regeneration:

   # plesk bin http2_pref --disable
   # plesk bin http2_pref --enable