Slight snag with that unfortunately. It's possible that the Ombudsman
might automatically close the case by default due to SoLR, since Symbio wouldn't be able to respond anymore and there'd be no guarantee of the case ever making further progress. Likewise, it's extremely likely that any new cases raised to the Energy Ombudsman about a failed supplier that has already triggered SoLR will be rejected, since it'd become a stalemate.
You may want to check the case status when you get chance. If it does get closed under that policy, then I'm afraid it'd be basically game over for the most part. Appointed Suppliers can opt to attempt to resolve these complaints, but there's no requirement to do so - and with no backstory available... It would be extremely difficult to resolve. The Ombudsman should be in touch regarding the next steps if they haven't already.
If that happens, the best I can think of might be to contact Symbio's administrators. If the case was closed in your favour or is/was still outstanding, then you could try
Symbio@azets.co.uk as they're dealing with Symbio's affairs.
Good luck