Mapped domains are showing a 403 error code

SLS needed.
I have tried all steps from this blog post: https://premium.wpmudev.org/blog/fixing-403-forbidden-error-wordpress/
1. Reverted .htaccess
2. Checked file permissions
3. Performed a conflict test
4. Downgraded Domain Mapping
5. Downgraded Wordfence as it was updated a little before this issue comes up
6. The configuration on the server has not changed, and the IP is not being blocked

Nothing worked.

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