Unable to upgrade elastic cluster to 6.8.0 and 7.1.0 from 6.7.1

Hello Together,

I was trying to upgrade my cluster from 6.7.1 to 6.8.0 and i have came across the below error.
Anyone have inputs on this.

Error:
The requested cluster configuration change is not permitted. Value of field 'elasticsearch.version' cannot be changed to [7.0.0].

When i checked in logs I could see the error as:

Deprecated field [_version] used, expected [version] instead
[es/i-10/es.log]

Can you provide more details?

Where are you getting that error?
What were you trying to do at the time?