Did you specify which financial category you were applying under on Appendix 2?
It sounds like because you did not supply all the required documents for Category F/G (self-employment) they seem to have assumed you were applying as exempt from meeting the financial requirements… which you aren’t and you wouldn’t have been applying as exempt anyway, since only UK sponsors receiving certain government benefits are exempt from meeting the financial requirement. Everyone else has to meet it.
Are you able to post the exact wording of the whole letter?
Sometimes there is more to the reason for the refusal than the part of the letter you think is the main reason, but it is worded in such a way that it isn’t obvious, so seeing the whole letter can help us determine exactly what the refusal was for and how it can be rectified.
