While adding sub-domain, I'm facing issue with POST request. I tried adding sub-domain, server is not accepting the POST request.
Solution -
1. Login to Plesk and Go to Tools & Settings > Web Application Firewall > Settings.
2. Select ModSecurity mode to 'Fast'.
3. Also, please open 'modsecurity.conf' file in 'C:\Program Files\ModSecurity IIS'.
4. Set - SecRequestBodyAccess Off
5. Restart IIS.
That's it! It resolved my issue.