Partner Event Sources in EventBridge not appearing for just 1 Region in 1 Account

We are trying to configure Partner Event Source in EventBridge. While we are able to generate Partner Event Source in Ireland region we are not able to do the same for London region. Nothing is happening in London Region when we trigger from partner sources. Not sure why this is happening just for 1 region in this particular account while it is working for other accounts and other regions as well

Thanks Visaka