The REST API encountered an unexpected result – Error

I am getting the error: “The REST API encountered an unexpected result”

Full Message:

The REST API is one way WordPress, and other applications, communicate with the server. One example is the block editor screen, which relies on this to display, and save, your posts and pages.The REST API call gave the following unexpected result: (404) <!DOCTYPE html> <html style=”height:100%”> <head> <meta name=”viewport” content=”width=device-width, initial-scale=1, shrink-to-fit=no” /> <title> 404 Not Found </title></head> <body style=”color: #444; margin:0;font: normal 14px/20px Arial, Helvetica, sans-serif; height:100%; background-color: #fff;”> <div style=”height:auto; min-height:100%; “> <div style=”text-align: center; width:800px; margin-left: -400px; position:absolute; top: 30%; left:50%;”> <h1 style=”margin:0; font-size:150px; line-height:150px; font-weight:bold;”>404</h1> <h2 style=”margin-top:20px;font-size: 30px;”>Not Found </h2>

The resource requested could not be found on this server!

</div></div><div style=”color:#f0f0f0; font-size:12px;margin:auto;padding:0px 30px 0px 30px;position:relative;clear:both;height:100px;margin-top:-101px;background-color:#474747;border-top: 1px solid rgba(0,0,0,0.15);box-shadow: 0 1px 0 rgba(255, 255, 255, 0.3) inset;”>
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</div></body></html> .

I have searched the internet and WPMUDEV for a solution. Some blame Defender, but this site doesn’t have that setting enabled. Some blame this plugin or that, all things that don’t match this site.

Please help with this error.