The server list is refreshed in the app itself, with the subscription refresh button. The link stays the same; only its contents change, so there is nothing to copy from your account again.
In HAPP and other clients this is a separate action next to the subscription profile: a refresh button, or "Update" in the profile menu. The wording differs a little from app to app, but it means the same thing: the client downloads the server list through your link again.
Reconnect afterwards. An active connection keeps running through the server you connected to earlier, so changes take effect on a new connection rather than by themselves.
Many clients can refresh a subscription on a schedule. If yours has that setting, turn it on and the server list keeps itself current.
Try importing the same link into another app from the list on the setup page. That separates a client problem from a subscription problem quickly: if the servers appear in the second app, the first one is at fault, so reinstall it and import the profile again.
It is also worth trying both protocols. The subscription carries VLESS Reality and Hysteria2 servers: the first disguises itself as ordinary HTTPS, the second runs over QUIC and holds up better on lossy mobile networks. Hysteria2 servers are marked Hy2 in their names, so if one option will not go, pick a server on the other protocol.