Port 53 is the default port for DNS traffic. If the firewall is blocking port 53, then users will not be able to resolve domain names and will receive errors stating that the website could not be located.
The other options would not correct the issue. Setting an explicit deny to all traffic using port 80 instead of 443 would block all HTTP traffic, not just web traffic. Moving the implicit deny from the bottom of the rule set to the top would make the deny rule more restrictive, which would not solve the issue. Configuring the first line in the rule set to allow all traffic would allow all traffic, including malicious traffic, which is not a good security practice.
Therefore, the best way to correct the issue is to ensure that port 53 has been explicitly allowed in the rule set.
Here are some additional information about DNS traffic:
DNS traffic is used to resolve domain names to IP addresses.
DNS traffic is typically unencrypted, which makes it vulnerable to eavesdropping.
There are a number of ways to secure DNS traffic, such as using DNS over HTTPS (DoH) or DNS over TLS (DoT).