If there are IP blocks - check the plugins that block spam like Sucuri and others.
Also, please check your .htaccess file as there are ways to block IP addresses and IP blocks via .htaccess.
To allow IP addresses, you can also add these lines to your .htaccess (BUT, prior to this, make sure that there are no plugins doing the oposite):
# ALLOW ALL REQUESTS
# Apache 2.2Order allow,denyAllow from all
# Apache 2.4+Require all granted
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And opposite, here is a sample of a .htaccess file to ban a range of IP addresses.
To ban a whole IP range, such as from 192.168.1.1 to 192.168.1.254, you can also do so by using an .htaccess file as seen in the below example.
Require all grantedRequire not IP 192.168.1allow from all
