HI Charles,
My suggestion would be to upload a blank file into the account and asset reference data in ITP, publish the blank files and update your reference data. Then start again with the account reference data and ensure your account reference data has the purchase and depreciation accounts in it. Publish that and then do the asset classes.
Sometimes starting again helps when there have been alot of updates.
Another thing to note is that you need to promote the data to production before importing to ITP (if you are using the integration)
Let me know if you still running into issues after the above,
Lauren Griessel