Hi @rosatigino93 and welcome to the Cayenne Community
Is your ESP8266 connected through our “Bring Your Own Thing” MQTT API? If so, this is a known issue with MQTT notifications being delayed or not arriving that we’re working to fix at the moment. If you have it connected ‘as an Arduino’ you should not see these delays as non-MQTT connected Raspberry Pi and Arduino devices use a different notification system that doesn’t have this issue.
If you already have your ESP8266 connected as an Arduino, then there may be a different root cause. I know some international users have had issues with SMS notifications as our system requires the number to be entered as if it was dialed from the USA. If this is the case, let me know what country you are in and I can show you the correct format to dial in.