However could not conclude on how this was working for last two and half years with those two restrictions and now what caused the restriction to be more stringent.
We also tried to create a new project and API key under https://console.cloud.google.com/apis by following the steps provided in the EmbedPlus document. However, even with the new key the issue persists.
We can still create 9 more project so this limit has also not reached.