I just reinstalled it again without changing any configuration except for the port, and the result is the same. The following is the log message:
---Ensuring UID: 99 matches user---
---Ensuring GID: 100 matches user---
---Setting umask to 000---
---Checking for optional scripts---
---No optional script found, continuing---
---Checking configuration for noVNC---
Nothing to do, noVNC resizing set to default
Nothing to do, noVNC qaulity set to default
Nothing to do, noVNC compression set to default
---Taking ownership of data...---
---Starting...---
---Checking for 'runtime' folder---
---'runtime' folder not found, creating...---
---Checking if Runtime is installed---
---Downloading and installing Runtime---
---Something went wrong, can't download Runtime, putting server in sleep mode---