There are a number of different errors that the Quality check will show. One of the errors you can encounter has the format 'condition'/'gender'/'availability' contains values that are not allowed.
Some fields can only contain certain values that are accepted by the export channels. Whenever there are values in a field that are not in the list of accepted values, you will see this error.
In the Finalize-step of your feed you can see the suggested values for the different fields. You will see a question mark behind the field name and if you hover your mouse over it, a window will appear with an example of what should be placed in the field. If the example contains a bracketed list, these are the only values the channel will accept.
If your values are different from the accepted values, you can replace them with the replace multiple values rule.