Lumo are clearly in the wrong here and must reimburse the customer.
Does this mean they should restrict ticket sales to there App, or do other retailers have to ask if you've check with Lumo's additional conditions for travel?
If Lumo are not prepared to adhere to the minimum standards stipulated in the National Rail Conditions of Travel then yes, their services should be withdrawn from industry systems, and they should not recieve any revenue sharing through ORCATS/Lennon.Lumo is an abomination. If they can't meet the standard conditions of carriage elsewhere on the railway, then IMHO their services should be excluded from general tickets sales. Lumo tickets should be limited solely to the Lumo app to prevent people falling victim to their service. To the OP I would recommend formally complaining to Trainline.