Can someone take a look and make sure I understand this right about reverse proxy

Preface: Yes I know not a whole lot but I'm trying. If someone could just take a look at this and maybe it will help me find what piece I am missing.

We have an internal server that needs to be accessed on the outside, but they don't want it actually touching the internet so we run it through the BIG-IP F5 LTM. The internal IIS has an internal IP and an external IP assigned. The DNS entry is bound to the External IP address. A lot of what I setup has been copied from a currently working site that utilizes this exact same process.

From my understanding the connection "route" is as follows:

Internet-->ExtIP-->F5virtualIP-->IntIP

The External IP gets natted on the firewall to the F5 internal IP of the virtual server, and then the F5 virtual server is linked to the actual internal server IP. We have access rules in place to allow public access to the external IP as well as the F5 IP. There are NAT rules in place that *should* point anyone going to the external IP towards the F5 address, and then through that to the internal server.

There's an F5 rule in place that redirects from http to https as well. Internally, on my work PC, I can navigate to the site via it's FQDN. Externally though, I get a Not Secure Site message(we haven't gotten the cert in place yet so that is expected), but then after a while of trying to load, we receive an ERR_CONNECTION_RESET page and it can't load.

I feel like there is something I am missing but I just can't think of what it is. If anyone has any ideas I will be eternally grateful. Thank you in advance.