Seeing the POS Cafe page fail to load inside Shopify admin, but it works perfectly on a different network or a phone hotspot? That means the app and Shopify are fine - something on the store’s network is interrupting HTTPS. This guide explains what’s happening and how to fix it quickly.

Example error shown when the browser cannot complete a secure connection from the store’s network.
What this error really means
The Chrome message you’re seeing appears when the HTTPS connection to go.poscafe.app
is being
blocked, reset, or “black-holed” by something on the path (usually the local router, firewall, or a filtering proxy).
A successful ping
only proves DNS + ICMP are okay - it does not prove that TCP/TLS on port 443 works.
Most likely causes (and quick fixes)
1) Path-MTU / MSS “black-hole” on the router or firewall
-
Symptoms: Some HTTPS sites (especially with larger TLS records) hang;
ping
works. -
Test (Windows):
ping go.poscafe.app -f -l 1472
and step down until it succeeds. - Fix: Enable MSS clamping on the WAN interface (e.g., 1452 for PPPoE; ~1360 for certain VPNs) or reduce WAN MTU.
2) SSL/TLS inspection or web filtering
- Symptoms: Loads on guest/hotspot; fails on staff VLAN.
- Test: Temporarily bypass the filter or add an allowlist entry.
- Fix: Disable SSL inspection for the domains below or allowlist them.
3) Proxy/device limits on URL length
-
Symptoms: Short URLs load; long
/install-or-render?...
URLs fail. -
Test: Visit
https://go.poscafe.app/
(short) vs. the long embedded-app URL. - Fix: Raise URL/query length limits or bypass the proxy for our domain.
4) IPv6 or QUIC/HTTP-3 quirks
-
Test: Force IPv4 with
curl -4 -I https://go.poscafe.app
; temporarily disable QUIC on the firewall and retry. - Fix: Prefer IPv4 for this destination or correct v6 routing; ensure UDP/443 isn’t being intercepted in a way that breaks fallback.
5) Security reputation block on the site’s public IP
- Test: Load the app on a phone using cellular data (Wi-Fi off). If that works, share your public IP with us.
- Fix: We can review/allowlist your IP on our edge if needed.
Fast troubleshooting checklist
- Open Chrome DevTools → Network → reload. Click the top Document request and note the exact error (e.g.,
ERR_CONNECTION_RESET
,ERR_SSL_PROTOCOL_ERROR
). - From a laptop on the store network, run:
nslookup go.poscafe.app curl -I https://go.poscafe.app curl -4 -I https://go.poscafe.app
-
MTU test (Windows):
If it fails, reduce the size (e.g., 1460, 1452…) until it succeeds - then set MSS clamping accordingly on the router.ping go.poscafe.app -f -l 1472
- Temporarily bypass any web filter/SSL inspection (or try a guest SSID/VLAN). If the app loads, add an allowlist.
- Try the same device on a phone hotspot. If that works, it confirms a site network issue, not the device.
curl
/ping tests - this lets us pinpoint the cause fast.Allowlist (no SSL inspection)
Add these to your firewall/proxy allowlist and exempt them from SSL interception:
-
*.poscafe.app
(especiallygo.poscafe.app
) -
*.shopify.com
,*.myshopify.com
-
*.shopifycdn.com
,cdn.shopify.com
FAQ
Ping works - so why won’t the page load?
Ping uses ICMP and tiny packets; your browser uses TCP 443 with TLS. Firewalls can pass ICMP but block or break large HTTPS packets (MTU/MSS issues) or decrypt/deny TLS (SSL inspection).
Is this a POS Cafe outage?
If the app loads elsewhere, it’s not an outage - it’s the local network path. The fixes above resolve it in nearly all cases.