I would need more information as to why this is happening or perhaps a picture.  Here are some possibilities so you can help me diagnose this.

1) Maple petiole borer can cause leaf drop.  See this article to see if this could be it

https://www.canr.msu.edu/news/maple_petiole_borer_causing_leaf_drop_in_maple_trees

2)  Spring storms can cause this

Sometimes spring storms also cause some maple leaves to drop. The best way to tell why the leaf dropped is to look at where the leaves came from. If you can still see a small petiole stub attached to the tree, it was most likely due to maple petiole borer. However, if the petiole broke cleanly at the base where it is attached to the tree, it was probably due to wind damage.

3)   Gray Squirrels

Gray squirrels

• Unusual numbers of complete, green leaves laying beneath the tree
• Whole leaf sections are removed from branches and dropped to ground
• Damage usually occurs in late spring, early summer

4)  Anthracnose

Anthracnose is a common fungal disease of sycamore, ash, maple, oak and other trees. Anthracnose is most severe in years with cool, wet spring weather. While anthracnose may cause extensive defoliation, it does not cause serious harm to healthy, well-established trees.

Symptoms of anthracnose on sycamores include brown blotches on leaves, death of young buds and shoots, and leaf drop. In cool, wet springs, affected sycamores may lose most of their initial foliage.

Can you take a look and provide me with more information to best diagonose this. Thank you

Hello again.  Have you reviewed the possibilities i outlined before.  Do you have any other information you can pass along so we can determine the cause of the leaf loss?

Since i have not heard back from you, i am closing this query.  You can open it again once you have more data