Hi,
my own IP-adress is locked out from my site. I get a 403 error.
I tried to deactivate the plugin via ftp, but still I cannot access the site.
How do I get access again?
There should be a way to unblock your IP but you would need to ask the developers of the plugin that has actually locked you out. My plugin does not use 403 errors to block IPs, so it must be some other security plugin you have installed that is doing this to you.
Try logging in from another IP, maybe use your phone (on your mobile data, not wifi), then you can deactivate that other plugin that is causing this issue.