There isn't any call stack/exception, only the log row:

"Could not invalidate region: null"

The source code in BaseRegion.java that logs the message does not supply the exception, only it's message - which is "null":
log.trace("Could not invalidate region: " + e.getLocalizedMessage());

But when debugging, you can see that the NPE occurs in the method: cacheAdapter.withinTx(), cause the transactionManager is null.

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