I attempted this last week (July 9) and we were turned away, as were several other people who were attempting a walk-in. We arrived at 8 am, the security guard let us through, and we waited for around 45 minutes, only to be told by an employee there that as of July 2, they were not doing walk-in appointments there. My guess is that due to the volume of appointments they had that day (there were several people there already at 8 am), they could not do any walk-ins.
We were told that we could come back the following day (July 10) between 2-4 pm, but that it was "first come, first serve." We didn't want to take the risk of being turned away again, so I am requesting an appointment at the Ottawa office instead. Just waiting to hear back. This may be a better option for you if Ottawa is your local immigration office.