Error occurred after migrating from Windows VM to Raspberry Pi 4: Timeout sending notification

I had recently install home assistant initially on a Windows VM (through VirtualBox). notify.notify was working fine at the time, but since I migrated the system to Raspberry Pi 4, I have been experiencing the following error and no notifications are sending to my iOS devices:

Timeout sending notification to https://mobile-apps.home-assistant.io/api/sendPushNotification

Did anyone experience this before?