So here I decide to post a new topic & describe it more clearly.
First, the problem that epic Arichvist can't 'eat' Epic Spell Seeds has been solved by Great xwarren:D I checked the scripts and found that Epic Archivist was forgotten in activate_seeds.nss(ncs)
But then... still there's another problem. It seems that if one has ONLY Archivist as the base spell caster class, nothing will appear in the Epic Spell Radial Menu after adding epic spells. This doesn't occur if the character has another spell caster class. For example, 20 Archivist/1 Runecaster and 20 Archivist/1 Fighter have this problem both, but 20 Archivist/1 Cleric or 20 Archivist/1 Warmage works well.
So I think there's something wrong that Archivist isn't treated as a spell caster class in the script which add epic spells to the radial menu. I tried to find the script but only got failure:| Could I get some help?
PS: I'm still using PRC 3.3H. Don't know whether it's fixed in 3.4.