Are you taking pictures in low light or low contrast situations. If so the camera may be UNABLE to lock focus that's why the camera has a built in LED AF Assist Beam. But when a speedlite is being and the ambient brightness is low. The speedlite will assist the camera's AF system using Intermittent Flash Firing the "IR (Infrared)" (not really IR just a red grid pattern) AF Assist Beam DOES NOT WORK ON ANY mirrorless camera system. Please post some pictures in the forum. What lens are you using. What settings are you using ISO & Aperture. You only listed a shutter speed.
Can you post an image along with what your camera settings were?
Since 1/500s is faster than the sync speed, assuming you had high-speed-sync enabled. Does the metadata for the captured image show it was indeed take with 1/500s?
12/05/2023: New firmware updates are available.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.