Have you made any changes in SJB core files?
If no then please deactivate the Job Board plugin and install a fresh version of Simple Job Board.
Let us know if the issue still persists.
Thanks & Regards,
PressTigers
Can you please deactivate all your plugins except Simple Job Board and activate any WP default theme like Twenty Sixteen etc and then view the job page. In this way, we can backtrack the issue.
Maybe, your theme is conflicting with our plugin.
Let us know if the issue still persists.
Thanks & Regards,
PressTigers
Have you switched your theme to any WP Twenty theme?
Thanks & Regards,
PressTigers