Genelde bu hatayı aşağıdaki kodu .httacces e ekleyerek çözüyorum.

# XML-RPC DDoS & TRACKBACK/PINGBACK PROTECTION
# Using this code blocks Pingbacks and Trackbacks on your website.
# You can whitelist your IP address if you use A Weblog Client
# or want to whitelist your IP address for any other reasons.
# Example: uncomment #Allow from x.x.x. by deleting the # sign and
# replace the x’s with your actual IP address. Allow from 99.88.77.
# Note: It is recommended that you use 3 octets x.x.x. of your IP address
# instead of 4 octets x.x.x.x of your IP address.


Order Deny,Allow
# Whitelist Jetpack/ Automattic CIDR IP Address Blocks
Allow from 192.0.64.0/18
Allow from 209.15.0.0/16
Allow from 66.155.0.0/17
Deny from all


Olmazsa şunu ekle

Allow from all

Veya

SecFilterEngine Off
SecFilterScanPOST Off