Printing envelopes froma data base

Having trouble accessing the mail out data base. I have been using this db for years to print club envelopes. I always open the envelopes format and then click print and everything has been OK in LO. This time I get an error message ‘the data source was not found, the connection to the data source could not be established. Please check the connection settings’. So I check the settings and select the db I want to use and ‘Apply’ and then get another error message ‘the date source does not exist’ ! Hmm frustrating - have spent literally hours trying to find out why this has happened now. Can anyone help me with this please. Treker 71