Hello @JonathanNightingale-6290
This appears to be known issue with VS extension, re: unable to deploy python app from VS code extension - ServiceUnavailable
If you're continuing to encounter this issue in your subsequent deployment attempts, we recommend opening a support case and working with a support engineer who has a deeper insight into your environment. If your subscription doesn't carry a support plan, we're able to grant you one (free of charge) for resolving this issue. If you'd like to opt for this, please send us an email at azcommunity at Microsoft dotcom
and we'd be happy to help :)