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The most common error I see happening with delegations is related to power downs. If you're powering down your balance, you can't delegate. But the connection issues could also be playing a part in it, if that's not the case.

Yes, that was it. I forgot I had a small power down going. Thanks for taking the time to reply.

How can we determine this in an rpc call? Hmm... I just canot help you test. I need to upgrade my machines first.