I tried to repro this same in my environment by creating a app deployment after provisioning the azure spring app. I got the same error as no app with that name available in the azure spring apps.
So before deploying to app we have to create an app in azure spring service. I used below command to create an app.
az spring app create --resource-group rg-group --service azspringappvjy01 --name azspringappvjy01-app01 --cpu 1 --memory 2Gi --min-replicas 2 --max-replicas 2 --assign-endpoint true
output: enter link description here https://i.imgur.com/NFiNSiz.png
Verify the app in azure portal in azure spring service.

Now deploy artifacts to the app created on azure spring service as below.
az spring app deploy --resource-group rg-group --service azspringappvjy01 --name azspringappvjy01-app01 --artifact-path target/spring-boot-complete-0.0.1-SNAPSHOT.jar --env testEnvKey=testEnvValue --runtime-version Java_11 --jvm-options '-Xms1024m -Xmx2048m'
output: enter link description here

Reference: Deploy azure spring app | Microsoft