I am not at all savvy to try an afl. But I will make amends by providing you a description of the steps.
In AMI, I drag and drop the custom plugin ("sandip") and then the gdfl plugin. I right click Parameters and edit the values like whether "sample strategy" is preferred (=NO) and "auto should be started" (=YES), client id, etc etc.. This was previously enough to start the semi trade by clicking the BUY/SELL button on the right corner as the signal arrows appeared. These steps are also enough to run the gdfl formula in semi without using my plugin at all.
I don't know if it answers your query but am ready to supplement.
Firstly, the easiest way out would be to seek support from GDFL.
Second, the point of decision is to determine where the chain of action is getting broken: 1) GDFL AFL to GDFL Plugin, 2) GDFL Plugin to Nest, 3) Nest passthru to Plus API, 4) N+ API to Nest Buy/Sell Order action. The suggested 3 line AFL would have tested the chain at points 3 & 4 (and some underlying aspect of 2).
Third, something has changed, and most likely at your end. If you cannot pinpoint it yourself, reinstall everything that GDFL has provided, and try again.
Lastly, it would be appreciated if you can take this discussion to another more appropriate thread; either the GDFL thread or the auto trading section.