Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. https://crt.sh/?q=example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.
I notice that all requests (including the challenge requests) are being redirected 301 to HTTPS.
I also notice that you state your web server is "Microsoft Windows"; which I can only assume to be some version of IIS.
But, however, the web server responding to the requests is shown as: nginx/1.16.1
So my first question is: What is the public IP address of your web server?
[we need to be sure global DNS is providing the correct IP]
My second question is: Which control panel are you using?
If he left no "instructions" then we have to guess or figure this out without them.
You would need to repeat his actions... But we don't know them.
OR
Create new similar action.
But you say you have no access to the system.
This I do not understand.
How are you expected to do this work without any access?
What access to the system do you have?