How did you find those symbols?

For example
AUDCAD = CS.D.AUDCAD.MT1.IP

If I search the markets API for AUDCAD:
https://demo-api.ig.com/gateway/deal/markets?searchTerm=AUDCAD

I only get two hits
CS.D.AUDCAD.CFD.IP
CS.D.AUDCAD.MINI.IP
you will also see that
"streamingPricesAvailable": true,

If I search for your symbol
https://demo-api.ig.com/gateway/deal/markets/CS.D.AUDCAD.MT1.IP
"streamingPricesAvailable": false,

So you need to go through your asset list and correct the symbol names.