Trying to create PDF of sales invoice..stating 'required table missing'

[kerzo]

HELP!! I'm using the Business Productivity Kit which came with Pro advanced 9. I apologize, but I am a complete beginner although I had previously been able to figure out some things. i am trying to email invoice -which I was able to do previously, but can no longer do this and a message comes up saying 'this action cannot be performed because the required table is missing'. I think I may have inadvertently changed some of the settings ?maybe relationships, but I can't figure out which. I would appreciate any input.

[IdealData]

This is far too vague - you will need to post the offending file on the board otherwise we cannot see what you have changed.