The "update_url" is not used by Firefox in the root of a manifest; your add-on will be updated via the Add-ons site and not your "update_url". See: https://mzl.la/25zqk4O
The "update_url" is not used by Firefox in the root of a manifest; your add-on will be updated via the Add-ons site and not your "update_url". See: https://mzl.la/25zqk4O