You mean someone took down a message for Luke and forgot to give him it?
Luke was in the shower for days while the Force phone was ringing?
I have no reason to think there's a delay between two Force callers when communicating with each other. All examples shown so far have been instantaneous.
The location of Moff Gideon was probably on the other side of the Universe, and it took Luke a while to get there. Space is big, but this is just pure speculation on my part.
But distance has never been an issue in Star Wars before. When they thought the Falcon had jumped to hyperspace in Empire Strikes Back they remark "it will be on the other side of the galaxy by now" only a short time later.
It's a long way and Luke originally went to Tython where he got the signal from Grogu from the ancient temple on top of a mountain. It wasn't until the Mandalorian and his crew located where Moff Gideon was did the New Republic know. When the New Republic found out, Luke found out.
I think you're wrong. The signal was sent from Tython. So Luke naturally went there first. They went on that mission to the mining colony find where Moff Gideon was. No one knew until the codes were recovered. Once they were recovered everyone knew. You're ignorant about things.
Rey was an adult who could send coherent messages like "The Resistance is on the plant Crait and need help THIS MINUTE!". Grogu was a toddler who can't talk yet, and his Force message was probably something like "Hungry wanna frog... blue light so peaceful... oh look shiny men! Friends like Mando!".
So Luke would maybe be able to get a fix on the location of the original call through some Force power that's never been explained to us, and then he had to track Grogu through hyperspace. The only way he could do that is by communicating through the Force with Grogu, and Grogu would never know where he was or be able to concentrate, what with being bled or tortured and so on. It's amazing it only took a week.