plugin error message

I'm getting the following error message on J!MailAlerts - JDownloads - Latest Files plugin (screen shot attached):

Table 'rimexco1_intranet.nx6ur_jdownloads_cats' doesn't exist SQL=SELECT cat_id , cat_title FROM nx6ur_jdownloads_cats

Can you shed some light on what it means, please?

Thanks!
Denise