The attached EA needs to subscribe to the two Symbol() strings declared, else order entry for one (or the other) fails.
Can you please confirm what MQL4 syntax is required in order to get both (or more than one) Instrument subscribed?

NOTE: this is just a simple MQL4 example that converts OK but then fails to run-
what I need to understand is the mql4 synatx required in order that I can subscribe to multiple Instruments -
OR is this not available in the conversion to .jfx ?

https://docs.mql4.com/marketinformation/symbolselect - this is the function you need.

Here is example of how your init function could look to make the strategy work:

int init(){
   lots=initiallots;
   dg=Digits;
   
   SymbolSelect(symbol1, true);
   SymbolSelect(symbol2, true);
   
   return(0);
}

But, unfortunately, there is some limitations of SymbolSelect usage in JForex:
1) you can't subscribe to instruments from indicators
2) you can't unsubscribe from instruments (for both strategies and indicators)

Thank you - this compiles OK, but I get:
Strategy tester: java.lang.UnsupportedOperationException @ jforex.converted.SimpleHedgerv104.init(SimpleHedgerv104.java:236)
on running in Historical tester.

This is Converter's bug. That bug is fixed in the next API release. It will be available on DEMO in the next few weeks.

As a temporary workaround, you can comment out SymbolSelect function calls and recompile before running strategy in Historical Tester, and it should work fine. But don't forget to select appropriate instruments in Historical Tester (Historical Tester tab > Instruments button).

Also you can avoid using programmatic subscribe via SymbolSelect and subscribe to instruments manually using Instruments panel on the left side of JForex Platform. In that case you can completely remove SymbolSelect usage.