It’s normal for red eyed treefrogs to sit motionless for hours on end given that they are a nocturnal species. I only see mine after lights out an that’s when he exhibits his darker coloration. An acclimation period of a few days is typical. But be advised that frogs do not typically respond well to handling. I’d realistically avoid any handling period unless absolutely necessary. Provide a shallow dish for soaking, a day and night cycle and just be patient. Also, kritter keepers are a less than optimal enclosure. You’d want to go with something more vertically oriented and be sure to add some cover such as live or fake plants or cork bark.