The most common culprit is the browser itself. Clear cache and cookies, then try again. If that doesn't help, disable browser extensions — ad blockers and script blockers frequently interrupt the connection test. Chrome and Firefox work most reliably; if you're on Safari, switching browsers often solves it instantly.
Before blaming the provider, check a few things on your end. Connect via Ethernet instead of Wi-Fi — wireless adds interference and distance penalties. Close background apps that consume bandwidth: cloud sync, streaming, system updates. Run the test two or three times and average the results, since a single measurement can be skewed by a momentary network spike.
High and unstable ping usually points to Wi-Fi congestion or a busy router. Move closer to the router or plug in directly. Also check how many devices are active on the network — a single streaming device can add 50–100 ms of latency. If spikes happen only at certain times of day, the issue is likely on the ISP side during peak hours.
On mobile, force-close the Speedtest app and relaunch it. If it keeps crashing, clear the app cache in system settings. Outdated versions sometimes lose compatibility with the current API — update through the App Store or Google Play. On Android, revoking and re-granting network permissions occasionally fixes silent launch failures.
This happens when the account session expires mid-test. Log out, log back in, and run a fresh test. If you're not logged in, results are stored temporarily and may disappear after a browser refresh — create a free account to keep your history persistent.