When using Wordfence and NitroPack simultaneously, make sure that NitroPack's IPs are whitelisted and removed from the blocked IPs list in Wordfence. We have a list of all NitroPack IPs that should be whitelisted here.
You can whitelist our IPs in the Wordfence plugin from the "Advanced Firewall Options" menu.
Image source - this article by contentstudio.io
Also, make sure that Wordfence hasn't blocked any of NitroPack's IPs. You can find the IPs blocked by Wordfence in the "Blocking" menu, under "All blocks for...".
Image source - Wordfence's official plugin page
If you find any of NitroPack's IPs here, make sure to unblock them.
Once all of our IPs are whitelisted and removed from the blocked list, you're set to use NitroPack and Wordfence simultaneously.