The region of Tappuah belonged to Manasseh, but Tappuah itself, on the border of Manasseh, belonged to Ephraim.

Joshua 16:8
From Tappuah the border went westward to the Brook of Kanah and ended at the Sea. This was the inheritance of the clans of the tribe of Ephraim,

Joshua 17:7
Now the border of Manasseh went from Asher to Michmethath near Shechem, then southward to include the inhabitants of En-tappuah.

Ezekiel 48:5
Ephraim will have one portion bordering the territory of Manasseh from east to west.

Now Manasseh had the land of Tappuah: but Tappuah on the border of Manasseh belonged to the children of Ephraim;