Your screenshot shows check marks next to Welcome, Lesson 3, and Thank You, so first check whether the lesson has already reported completion. Close the training player using its window close button, return to the course curriculum in AMD Academy, and refresh that page. The curriculum status is the useful check; a separate Complete Lesson button may not appear on every player screen.
If Lesson 3 still shows incomplete, reopen it, let the lesson finish normally, and continue through the final Thank You screen before closing the player. If the final screen is blank, try the player fullscreen control or reduce browser zoom to check whether a bottom control is outside the visible area.
Does the curriculum show Lesson 3 as Complete after closing the player, or is it still In Progress? That would help distinguish a missing display control from a progress-tracking issue.