Can you cast a spell with convoke and tap a creature that has summoning sickness to pay for it?

Convoke (CR 702.51) allows you to tap creatures you control as you cast a spell to reduce its cost — each tapped creature pays for one generic mana or one mana of that creature's color. Crucially, tapping a creature for convoke is treated just like paying a cost that includes the tap symbol (T).

Summoning sickness (CR 302.6) prevents a creature from attacking or being tapped to pay costs using the tap symbol unless it has haste or has been under your control since the beginning of your most recent turn. Because convoke explicitly uses the tap symbol as part of its cost-payment mechanism (CR 702.51a), the same summoning sickness restriction applies.

There is one important exception: if the creature has haste, summoning sickness does not apply (CR 702.10), so you can tap a creature with haste for convoke even if you just played it this turn.

Concrete example: You play a Llanowar Elves on your turn (no haste). On that same turn you try to cast Chord of Calling and want to tap the Elves to help pay. You cannot — the Elves have summoning sickness and may not be tapped for convoke. If instead you had played a Rampant Raptor (which has haste), you could tap it immediately for convoke.