Description:
When trying to retrieve tags from a PLC, the Ewon logs an error "S74srv-Invalid DataType in read response" and tags value don't change.
Solution:
It is important to release the access to the PLC when there is no longer a need for it. To do so, you need to go in the TIA Portal software and activate the the “PUT/GET communication” feature.
The “release access” command is represented by this checkbox in TIA Portal: