@jedrb 

When Pega Platform and the client use OAuth 2.0, they negotiate a token that allows the client to access Pega Platform for a defined period.

OAuth 2.0 authentication is a token-based authentication(OAuth 2.0 Client Credentials details might be expired)

In Security-->OAuth 2.0 Provider The Pega Platform keystore stores the client's private and public key pair, which the server uses to authenticate the client machine.So could you please regenerate the client credentials (client ID and client secret) to the external application as a part of the authorization header is used. OAuth 2.0 client registrations The grant types supported by Pega Platform OAuth 2.0 clients are authorization code, client credentials, password credentials, JSON Web Tokens (JWT) bearer assertion. You can use these grant types alone or in combination with each other. 

In the Secure protocol configuration section, in the Lowest allowable SSL/TLS version field, select the SSL or TLS protocol version that you want to use to securely connect to the external application by using OAuth 2.0.

1. As per the Logs which you have caught the issue is related in configuring a Keystore by using a URL reference

for example: https://www.pegasystems.com/prweb/PRRestService/keys/v1/jwt/JWTGenerationProfile.

So Keystore types is JSON Web Key (JWK) which is caught in logs

please ensure that the refresh strategy for your Keystore 

• Reload once per interaction – Disable caching of the keystore file.if the keystore might change unexpectedly.
• Cache keystore (default) – Cache the keystore, with the caching time set to 3600 seconds. You can override the caching time in the Reload after field.

@jedrb Did you ever resolve this issue? I'm running into the same problem.

Except it only happens when I try to run the datapage, and it doesn't happen when other people with the same admin role and access as me tries to run the same datapage.

In the 2nd Error it is OAuth authorization grant error due to incorrect passing of parameters so, provide additional parameters that might be required by your OAuth 2.0 provider, in the Additional endpoint parameters

• Authorization code
• Access token
• Revoke token
• Refresh token

Due to which Pega is unable to create a fresh access token Causing OAuth 2.0 authorization grant error. hence the OAuth2.0 Authentication failed.

Hope this will gives u a better understanding and would resolve the issue.

Thanks || Duvvala Swathi