SharePoint 2019 - Office Online Server Error

[nawaftahir]

Hi Guys

I have deployed SharePoint 2019 and configured Office Online Server to allow SharePoint files to open in Browser. Here's the HA architecture

1- Front End + Distributed Cache Roles x3 Servers (Load Balancer)

2- Application + Search Role x3 Servers

3- MS SQL ALWAYS ON Database x3 Servers

4- Office Online Server x3 (Load Balancer)

The issue I'm facing is with opening SharePoint/OneDrive Files in Browser. Sometime, it works well but most of the time, following errors show up

'We're sorry. We couldn't open your workbook. You can try to open this file again, sometimes that helps.
''You do not have permissions to open this file in the browser.'

Tried all workarounds, used single tier approach but none worked.

PS: All Servers are in same Subnet with full access. No Firewall in between

[#2]

Hi nawaftahier,
did you get rid of your OOS problem?
I'm facing a similar problem here with a much simlpier setting (1 WFE+DC, 1 APP+Search, 1 SQL, 1 OOS):
Every day the Application Pools of the WebApplications have to be recycled on WFE manually to make OOS work.
What did you do to solve your problem?
Thanks for your reply!