Disappointment from Innovation group

They declined our claim for the gearbox because we had our clutch kit fixed just two months ago. Although the gearbox issue is not related to the clutch and falls outside the coverage policy, they still denied our claim. After numerous calls, they decided to send an assessor to inspect our car. The assessor stated that the gearbox ran out of oil due to an oil leak from the driveshaft. However, they could not confirm that this leak was connected to the recent clutch repair. Despite this, they still used the fact that we had the clutch fixed two months ago as their reason for denying the gearbox claim. I do not understand how a separate component can be linked to the other when they cannot establish a connection between the damage and the clutch.