Thank you anyway, but I already changed my settings. 

We will monitor this to see if glitches again.  We have been sending the invoices with attached .pdf files since we migrated our data to QBO from QBD a couple of months ago.  Honestly, the setting is several steps deep, so no one could accidently change it and only 2 people have access here.  It's obviously this known issue rearing its ugly head 4 years hence.