Hi @howard.kidd

If you are consuming Refinitiv Real-time feed data (e.g. ELEKTRON_DD service) then a couple of SymbolList RICs you can try - to see example format - is .AV.L and .AV.O.
Note that these are just example SymbolLists for demo purposes - I am not a content expert, but Refinitiv does not publish any particularly useful SymbolLists that I am aware of.

And the above will only work if the SymbolList domain has been enabled on whatever service you are consuming from. Looking at your initial post above - the SymbolList domain is not supported on whatever service you were consuming from.

If you are consuming an internally published service - which is what TRFX_MDFD_Symbols - sounds like, then you need to speak to your Market Data team / the publisher of the above service to get a list of valid SymbolList RICs. Certainly the status message. "Invalid asset class" -is not one I recognise as a Refinitiv-generated Status Message.
Refinitiv does not determine or have sight of what SymbolLists a client chooses to publish on their own internal services.

Hello @howard.kidd

Thank you for contacting us. Can you let me know if you are connecting to your locally deployed RTDS?

The domains (SymbolList is the domain) are provided by the source/service. The "No servers available that support this domain." error message indicates that from the service that you consume, for the instrument you are requesting, the SymbolList domain is not available.

If you are connecting to your locally deployed RTDS, you need to contact your Market Data team to verify which service(s) in your environment has the SymbolList data domain.