New Tier added - Enable Network Topology Errors out

[CristinHolmgren2]

I added a new tier to my existing network and now am unable to rebuild the Network Topology.  I received the ERROR 999999 code, so am stuck as to how to troubleshoot this.   The message all of a sudden now says, The spatial index was not found for Structure Junction.  How would adding a new Tier effect the spatial index of the Structure Junction?

[COI-GWEST]

You are most likely receiving this error because data was already appended to your UN feature classes.

• Tiers should be added before appending data in the utility network feature classes. If data is appended before adding a new tier, an error will occur.

https://pro.arcgis.com/en/pro-app/latest/tool-reference/utility-networks/add-tier.htm