Are there any errors in logread when restarting the interface, like with ifup wg0
Or debug it by editing /lib/netifd/proto/wireguard.sh and check the generated config in /tmp/wireguard/wg0.conf
diff --git a/package/network/utils/wireguard-tools/files/wireguard.sh b/package/network/utils/wireguard-tools/files/wireguard.sh
index 63261aea71..cb4be373f8 100644
--- a/lib/netifd/proto/wireguard.sh
+++ b/lib/netifd/proto/wireguard.sh
@@ -139,7 +139,7 @@ proto_wireguard_setup() {
${WG} setconf ${config} "${wg_cfg}"
WG_RETURN=$?
- rm -f "${wg_cfg}"
+ #rm -f "${wg_cfg}"
if [ ${WG_RETURN} -ne 0 ]; then
sleep 5