Found this on bezinga:

Companies may have some market-moving announcements such as M&A, capital raising, etc., to be made around the conference schedule.

The company in question may have some pressing agenda around the time that could take precedence over the benefits of meeting with investors.

https://www.benzinga.com/general/education/16/12/8780650/why-stocks-move-when-execs-cancel-presentation-appearances

I also found a book on how to run an effective IR dept which says in part.

..."never ever cancel a scheduled presentation, even if there is an excellent reason for doing so.  Following a cancellation, investors will think that something has happened with the company that management wants to hide, and will have a predilection to abandon the stock, or perhaps even sell the stock short"....

https://books.google.ca/books?id=hVKNvWHeZn4C&pg=PA163&lpg=PA163&dq=why+cancel+an+investor+presentation?&source=bl&ots=X-HrFXpV_k&sig=qSg1Sz5voK3GIyyWKQuQP5YlWy8&hl=en&sa=X&ved=0ahUKEwi22ov8jIrUAhVM5YMKHdVCB2sQ6AEIOjAD#v=onepage&q=never%20ever%20cancel&f=false

That book was written by a guy named Steven Bragg, and it looks like he has some solid bona fides:

STEVEN M. BRAGG, CPA, has been the chief financial officer or controller of four companies, as well as a consulting manager at Ernst & Young and an auditor at Deloitte & Touche. He received a master's degree in finance from Bentley College, an MBA from Babson College, and a bachelor's degree in economics from the University of Maine. He has been the two-time president of the Colorado Mountain Club, is an avid alpine skier and mountain biker, and is a certified master diver. Mr. Bragg resides in Centennial, Colorado. He is also the author of Accounting Control Best Practices and Accounting Policies and Procedures Manual (both published by Wiley).