The following error occurs when the debugger connects to a C2834x device:

C28xx: Error initializing flash programming: Interface returned from dll, but flash is not available on this device

C2834x devices do not have internal flash so CCS should not be trying to use the flash DLL. The connection succeeds and there are no issues loading the program (to RAM).

Another user provided the additional data points:

Attempting to load a simple hello world program into a TMS320C28346 with a XDS100v2:

CCS 8.2.0.00007 with Debug Server 8.2.0.1409 and TI C2000 Device Support 4.2.7.0 there is no error.
CCS 8.3.0.00009 with Debug Server 8.2.0.201810301800 and TI C2000 Device Support 5.0.0.0 results in the "C28xx: Error initializing flash programming: Interface returned from dll, but flash is not available on this device." error. When manually launching a debug session it is the act of connecting to the target which generates the error, not the loading of the .out file.

With CCS 10.2.0.00009 confirm that is the act of connecting to the target which generates the error, not the loading of the .out file.