Why is a location of birth which is correct and verified by a parent, shown as not being a "standardized" entry, and how is that corrected?
Please share a person ID so we can take a look.
It just means that the entered placename has not yet been associated with an entry in FamilySearch's Places database.
A bit more detail: FamilySearch's Family Tree uses a two-part structure for dates and places, where all such conclusions have both a display value and a standardized value. The display value is what is shown on a profile's Details page; it is often the same as the standardized value, but doesn't have to be. For example, it is possible to add more detail (such as a street address), or to leave out confusing parts of the jurisdiction. The standardized value is a label for a particular database entry (date in history or point on the map); for places, it is composed of a set of jurisdictions, from smallest to largest, which uniquely specify that place. Since administrations change over time, many places have multiple standardized labels, each appropriate to a specified time period, but it doesn't actually matter which label you choose, as long as it points at the correct point on the map.
Here is a Help Center article on entering and standardizing dates and places: https://www.familysearch.org/en/help/helpcenter/article/how-do-i-enter-dates-and-places-into-family-tree
Why is Oklahoma Territory no longer allowed in the use with location names? It use to work but now it does not and it started maybe a month ago.
Note: It use to work just fine with places like Roger Mills, Oklahoma Territory and not it does not even appear in the dropdown of allow known place names.
This was an administrative decision to simplify linking standards. See: https://www.familysearch.org/en/help/helpcenter/article/when-did-familysearch-combine-us-states-and-their-historic-territories-in-familysearch-places
Keep in mind that if you personally still want to include Territory in the place name, you can and there is no reason not to. Just enter the place name like this:
This is correctly entered and as you can see by the green check mark, this is correctly standardized. You won't have a map pin on the profile page, but that does not matter in the least. Everything still works just fine, including mapping.