I have been lucky and have not had an issue with this - however our federation skype chat is filled with people with this issue.
I haven't had the issue that you are currently having, however for like three weeks I was unable to use any of my energy recharge spheres. Often times when there is an issue (with any given area, not just with guardians) without an apperent cause it seems to fix it self after a period of time. I know this doesn't really help, especially when we are right in the midst of a guardian tournament. Not to mention that, in my opinion, these tourneys are basically the only type in which it is actually possible to get more out of it (in rewards) than you put in. Good Luck.
XPHello!
This issue is already discussed in another topic. Here is a link for you.
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