I just noticed the same thing after using it. Not sure if there is an official button to use, as I didn't find one, but going into your equipment and selecting the circlet will allow you to undo the charge.

Wondrous item, uncommon. While wearing this circlet, you can use an action to cast the Scorching Ray spell with it. When you make the spell's attacks, you do so with an attack bonus of +5. The circlet …

Circlet of Blasting Wondrous item, rare (requires attunement) This headband of twisted, multicolored wire aids spellcasters in unleashing their favorite destructive blasts. Three times per day when the …

Wondrous item, uncommon While wearing this circlet, you can use an action to cast the scorching ray spell with it. When you make the spell's attacks, you do so with an attack bonus of +5. The circlet …

Circlet of Blasting [1] [2] Magic Wondrous Item, Uncommon Treasure Type: Arcana Magic Item Plan (Artificer Level): 10+ While wearing this circlet, you can cast Scorching Ray with it (+5 to hit). The …

While wearing this circlet, you can use an action to cast the scorching ray spell with it. When you make the spell's attacks, you do so with an attack bonus of +5. The circlet can't be used this way again …

Wondrous Item, Uncommon. While wearing this circlet, you can cast Scorching Ray with it (+5 to hit). The circlet can’t cast this spell again until the next dawn.