Hi, I also had issues this morning deploying my shiny app to shinyapps.io. Can you check that your rsconnect package is up to date? It should be version 1.0.1 and above.
See https://forum.posit.co/t/notice-posit-cloud-shinyapps-io-dropping-support-for-rsconnect-1-0-1/172078 for more details.