Total amount not populating for online form
From what I can see, it looks like you're not using a price set - so it's actually a mystery why "Total Amount" appears in the first place.  You don't have anything to total!  I just confirmed on a test site that I don't normally see "Total Amount" on a contribution page that doesn't require it.

If you could edit your question to display a screenshot of the price configuration for this contribution page, perhaps someone will notice something amiss.