Some silica gel comes with an indicator to indicate when its ability to absorb water is exhausted. Yours apparently does not have the indicator. Just assume it is expired.
You can regenerate it by heat, see the Wikipedia link. Although it is most likely the material you have is silica gel, be aware that some drying agents, most importantly calcium chloride, cannot be regenerated simply by heating. Calcium chloride will be opaque white crystals, like coarsely ground chalk. Silica gel will be somewhat translucent.
John
Edit: We cross posted. Yes, regenerate the silica gel.