@infinitemac I have been able to reproduce; I see a lot of HTTP 404 error into the logs by getting most of our extensions, meaning "not found" from HTTP protocol while extensions are here and manual install is possible...
Since "extension pack" support from VSCode looks unstable for now there is no easy way to get the list.
You could eventually install the pack and check within local metadata in _userDir_/.vscode/extensions/stmicroelectronics.stm32-vscode-extension-3.6.3/package.json, but pasting here the list for you:
"extensionPack": [
"STMicroelectronics.stm32cube-ide-core",
"STMicroelectronics.stm32cube-ide-bundles-manager",
"STMicroelectronics.stm32cube-ide-build-cmake",
"STMicroelectronics.stm32cube-ide-build-analyzer",
"STMicroelectronics.stm32cube-ide-project-manager",
"STMicroelectronics.stm32cube-ide-debug-core",
"STMicroelectronics.stm32cube-ide-debug-generic-gdbserver",
"STMicroelectronics.stm32cube-ide-debug-stlink-gdbserver",
"STMicroelectronics.stm32cube-ide-debug-jlink-gdbserver",
"STMicroelectronics.stm32cube-ide-rtos",
"STMicroelectronics.stm32cube-ide-registers",
"STMicroelectronics.stm32cube-ide-clangd",
"eclipse-cdt.memory-inspector",
"eclipse-cdt.serial-monitor",
"ms-vscode.cmake-tools"
]
For the rest we need some hint from the Marketplace owner.
UPDATE: the issue is under analysis and tracked by https://github.com/microsoft/vsmarketplace/issues/1454