Sending direct messages to mentors is not encouraged and mentors are not obligated to respond.
Sending direct messages could not only overwhelm specific mentors, but also defeat the purpose of a public forum where learners benefit from similar errors/problems encountered by others.
If required, the mentor or staff will themselves initiate the direct message (e.g. in cases where they need to check your code to get a better understanding of the issue at hand).
Please post your queries as topics under relevant course categories so that it increases the visibility across our pool of mentors, staff and other learners , who can address your query much faster.