I had this happen to me at a company that is now an IBM subsidiary. I took FMLA leave to get mental health help to cope with the burnout, and about a week after I got back, they took me into an office for a "quick catch-up meeting" where they told me it wasn't working out and that I had to go. I'd worked my balls off, getting promoted directly from product support up to software engineering within a year, but apparently that didn't indicate anything positive to them.