Network & Connectivity Issues

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 of a network-specific loading error in Shopify admin 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):
Terminal window
```
ping go.poscafe.app -f -l 1472
```
If it fails, reduce the size (e.g., 1460, 1452…) until it succeeds, then set MSS clamping accordingly on the router.
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.

Allowlist (no SSL inspection)

Add these to your firewall/proxy allowlist and exempt them from SSL interception:

*.poscafe.app (especially go.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.