It's hard to disagree with anything Mentorman has said, however, Section 85 of the Local Government Act states:
...if a member of a local authority fails throughout a period of six consecutive months from the date of his last attendance to attend any meeting of the authority, he shall, unless the failure was due to some reason approved by the authority before the expiry of that period, cease to be a member of the authority.
In the absence of further clarification, I take this to mean calendar months, so 5th March to 5th September is six months. I don't recall seeing any relaxation of Section 85 in the temporary Covid legislation. The key to avoiding this is "before the expiry of that period." At the Zoom meeting in July, you should have approved the absence of anybody unable to attend.