Was Paine present at the Constitutional Convention in 1787?

No. With Franklin, Paine took part in the Society for Political Enquiries before the Constitutional Convention to prepare the political ground for a democratic constitution. But Paine was kept away from the Convention because of his numerous essays denouncing the bicameral approach to government and supporting universal suffrage, an end to slavery and complete democratic structures. The tide in America had turned against the radical principles of the Declaration of Independence, and Paine looked to Europe for the next tide of Revolution. He left again for Europe in the Spring of 1787.