Hello,
After further testing I found that this functionality does work. Here's a couple things to check:
1. What is your "work date" located under the gear button, click My Settings.
2. Go to your Item with the extended text and open your extended text to verify that your start and end date of your extended text includes your work date and make sure all sales docs are marked.
The date discrepancy is where I found my issue, my work date was 4/12/2016 and my start and end dates were 1/1/2017 and 12/31/2017. Once I changed my start and end dates (or removed them) then the Insert Extended text worked on Orders and Invoices that I tested.
3. Also, make sure you also enter the quantity for the item in order which will save the line.
Please let me know if this does not help resolve this issue for you.
Regards,
Jennifer Reinhardt
Please see our Dynamics 365 Financials Support Team Blog for helpful information:
blogs.msdn.microsoft.com/dyn365finsupport
