Internet calendar does not sync

Hi,

 I have outlook 365 installed on my laptop in which I have multiple email accounts configured. Some of these emails are O365 based official email ids which others are Gmail email ids.

I have subscribed google calendar in outlook as per the instructions given in https://support.microsoft.com/en-us/office/see-your-google-calendar-in-outlook-c1dab514-0ad4-4811-824a-7d02c5e77126

However, the google calendar does not synchronize or at best is erratic. No amount of refresh and outlook restart helps to synchronize gmail calendar with other devices.

I observed that the issue is coming in following scenarios: 

1. When I add an appointment in gmail calender on outlook, which never shows up in my phone. Often, these entries disappear entirely from outlook calendar. 

2. When I add an appointment on phone, sometimes it shows up on outlook but later it disappears. 

I even tried replacing htts:// with webcal:// while adding internet calendar, but it did not solve the issue. 

Any solutions? 

Thanks,