Work through these in order. The first two account for most reports, and cost nothing to check.
1. Is your service active and does it still have data?
- A suspended or out-of-data service will fail to connect even when the app looks correctly configured.
- Renewing does not reset your data allowance for the current cycle — see I already paid, why can't I use it? and What to do when the data is used up?
- Data resets on a fixed cycle, not on the 1st of the month — see When does the data reset?
2. Are you using the right node for where you are?
- IPLC/IEPL nodes are dedicated to mainland China. Outside mainland China they will not work — use a Global, HAYABUSA or FAST node. See I can't use from outside of mainland China.
- Node names indicate type and region — see Meaning of node names.
3. Is the correct service selected in the app?
- If you hold more than one service, the app must point at the active one and its subscription link must be current. See Correspondence between Apps and Services and Unable to update subscription.
4. Is your device clock accurate?
- A clock wrong by more than a couple of minutes stops connections on several protocols — see Why can an incorrect system clock prevent VPN connections?
5. Connects, but no internet?
- Check your device clock, restart the client, then restart the device — full steps in Can't Connect to Server Node? Connected but No Internet?
6. Still stuck? Find your client
- sing-box: Windows/Linux · iOS · Android · macOS
- v2rayN on Windows: v2rayN has stopped working · configured but no internet
- Shadowrocket on iOS: connected but no internet
If none of this resolves it, open a ticket and tell us: your platform, the client app, the node you selected, and what the client log says. That gets a real answer on the first reply instead of the third.