Work through these five steps in order — most connection problems fall to the first two. One: refresh your subscription inside the client; node details change over time and a stale list is the most common cause. Two: switch to a different node; individual nodes get maintenance windows, and the pool is maintained around the clock.
Three: check your mode — return-route users need Global mode (see our explainer on why Global mode matters). Four: quit the client fully and reopen it, or reboot the device, to clear stuck network state. Five: swap networks (Wi-Fi to mobile data or vice versa) to rule out local network restrictions.
Still stuck after all five? Tell support which step failed and what the error said — that single sentence usually pinpoints the cause.