Unable to trigger my Speedlite YN565EXIII via optical trigger using a Canon 750D (Rebel T6i)

I own a Rebel T6i and a apeedlite, a Yongnuo YN-565EX III. I’ve tried several times to trigger the flash off-camera (on a tripod with a softbox) and I’ve had some very unsatisfactory results.

With the speedlite on a tripod I’ve set it to ETTL slave mode (Sc mode). On the camera on the camera I went to Flash Control >Built-in flash settings in there I’ve set the following settings:

• Flash firing: Enable
• E-TTL II meter: Evaluative
• FLash sync. speed in Av mode -> 1/200
• Channel: 1
• Group: A

Here’s a image of the flash settings as it is right now:

On Built-in flash settings I have the following:

• Flash mode: E-TTL II
• Wireless func: (Set to the icon of the dedicated flash only)
• Channel: 1
• Firing Group: All
• Exp. Comp: 0

Here are some images of my camera settings:

First screen:

Second screen:

I have the sensor turned to me as I take shots of my speelite on a tripod. I’m literally taking pictures of the optical sensor:

Here’s how the speedlite is positioned:

I think it’s important to say that I’m shooting on full manual mode. Now to the problems.

1. Most of the times when I use the pop-up flash to trigger the speedlite, the built-in flash goes off, but the speedlite isn’t triggered, even though I’m pointing the built-in flash directly at the sensor at a distance of around 1.5 meters (about 5 feet I guess). The speedlite goes off on an estimate of one time every ten attempts. The batteries are new and I wait about 5 seconds between each new attempt.

2. When the speelite goes off, most of the time it doesn’t affect the exposure of the image. It’s like, it’s out of sync with the camera or something like that. My room it’s pretty dark, and even when the speedlite goes off the image is completely dark.

3. Sometimes (a good amount of times) the pop-up flash of my camera doesn’t go off even though it’s set to go off and my room is completely dark. Does the built-in flash have a recharge time or something like that?

I’ve also tried using the speedlite (and built in flash) on manual slave, instead of E-TTL slave, but had the same problems.

I’m trying to learn off-camera flash techniques and I was relying on the optical trigger, as I don`t have a wireless one, so if anyone has a suggestion on how to fix this I’m eager to try.