Resource Type Not Found in v1.6.3 while it works in v1.5.7


I build a provider that declares a resource like this:

resource "example_bag" "bag1" {
  name 	  = "res1"
  content = [
    book 	= "How to draw"
    pen 	= "Color red"

When I run terraform apply, with terraform version 1.5.7 it works but when I run with the new version 1.6.3 it says this error:

│ Error: Resource Type Not Found
│   with example_bag.bag1,
│   on line 20, in resource "example_bag" "bag1":
│   20: resource "example_bag" "bag1" {
│ No resource type named "example_bag" was found in the provider.

Has version 1.6.3 changed on how to declare resources? Can you give me some hints on what to investigate?