Well let's try to restore to the default search providers:
-with Firefox open this page: about:support
-click "Open Directory" to open your profile
-delete the files search.json, search-metadata.json and search.sqlite (if present)
-reboot firefox and those files will be recreated.

Does that issue still occur?
posted by <hidden> • 2 years and 10 months ago Link

I have this issue on two machines and tagawa reported he has the same issue, so it is probably an issue of DDG.
posted by clel 2 years and 10 months ago Link