Compelling to appear for personal hearing while on medical leave.

My husband is working with a PSU bank. He was served charge sheet and after enquiry a show cause was served with proposed penalty. He was given an opportunity for personal hearing as per bank rules. He could not attend the hearing as he was diagnosed with coronary heart blockage and the hearing was postponed on request of my husband. My husband is also suffering from diabetes since 1996 and also from depression. His age is 58. In the second week of April 2021 he tested positive for Covid-19 infection and struggling to recover from complications of corona due to his fragile health. Yesterday the employer(Chairman of the Bank who is disciplinary authority) sent a mail to attend through video conference but my husband expressed his inability to attend video conference. On this the employer asked to submit a written reply otherwise they will proceed against him. My husband is not in a position to even prepare a written reply as he is not fit mentally and physically due to corona and other ailments, the proofs of which were sent to the authorities. He will also lose the opportunity of personally explaining his case. I failed to understand why the authorities are in a hurry to punish my husband. Please guide what can be done in this situation