"Invoice failed to pay"

So not the swap in itself failed, but the payment to the invoice you were generated.
That means:

• was your Zeus node in persistent mode ? Why is good to put it in persistent mode in cases like this? So the LND service stays online, even if you switch the screens until the swap is finished. Remember that if your LN node goes out of sync, the LN invoice cannot be paid.
• was your Zeus node well synced and channels online with enough inbound liquidity to receive the amount from that invoice?
• did you create the LN invoice with route hints so the payer could find the correct route towards your private node?
• did you tried also other different swap providers ? You can switch to multiple ones in the same interface, not just Olympus.