OP actually held a refundable ticket. Thus, the entire Covid-19 situation is even less relevant. He may cancel for any reason or no reason at all and LH sold him a ticket on that basis.
Bottom line is that a refund should be initiated in 7 days. OP cancelled on 6 March and there is no reason for him not to have initiated a chargeback on the 8th day, e.g. 14 March. Almost a month later now.
Anyone due a refund who does not receive one ought to initiate a chargeback on the first day after it was due and has either not been paid or has been declined.
Consumers are not credit facilities and many need that cash as well.