Update 25/8/2020: This issue has been resolved with the release of AccountRight 2020.3
The LastModified field was added to the Sale/Invoice, Sale/Order & Sale/Quote AccountRight API endpoints in the AccountRight 2019.3 release. This field enables users to track the most recent update to time and date records and allows greater flexibility in filtering.
Creation of a new sale invoice, order or quote triggers an automated LastModified value however, the LastModified value doesn't get updated when updating an existing record via AccountRight and the API PUT method.
We apologies for any inconvenience due to this issue and the root cause is currently being investigated. Further details to be announced when the fix is to be released.