TimThumb Error

The following error(s) occurred:

• You may not fetch images from that site. To enable this site in timthumb, you can either add it to $ALLOWED_SITES and set ALLOW_EXTERNAL=true. Or you can set ALLOW_ALL_EXTERNAL_SITES=true, depending on your security needs.

Query String: src=http%3A%2F%2Fwww.extension.seohoo.com%2Fwp-content%2Fuploads%2F2018%2F10%2Fphoto_2018-10-28_13-59-14.jpg&w=90&h=64&zc=1
TimThumb version: 2.8.14
Instruction: Thumbnails don't work — what to do? (registration required)