Thanks!
In the end, I ended up setting up the webflow site on a different subdomain (wf.canimmunize.ca), which allowed the domain to be properly connected to that subdomain. And then I proxied my desired domain to that subdomain like so:
location /en/privacy-policy {
proxy_ssl_server_name on;
proxy_redirect https://wf.canimmunize.ca https://www.dev.canimmunize.ca;
proxy_redirect http://wf.canimmunize.ca https://www.dev.canimmunize.ca;
proxy_pass https://wf.canimmunize.ca$request_uri;
}