Are you confident those are the specs of a 2018 MacBook Pro?
As a test: Go to the menu File > Project Settings > General and set the Renderer to Software Only.
Does the problem remain?
Thanks for replying, Meg!
Changing the renderer does not fix the problem. I tried the other two (Metal, and OpenCL), and they do not fix the problem, either.
As for the specs, yes I'm certain. But here are some more granular details on the hardware:
Model Name: MacBook Pro
Model Identifier: MacBookPro15,2
Processor Name: Intel Core i5
Processor Speed: 2.3 GHz
Number of Processors: 1
Total Number of Cores: 4
L2 Cache (per Core): 256 KB
L3 Cache: 6 MB
Memory: 8 GB
And the graphics:
Chipset Model: Intel Iris Plus Graphics 655
VRAM (Dynamic, Max): 1536 MB
If you create a new project and new sequence, does the problem remain?
Was this a project that has been upgraded from a previous version of Premiere Pro?
In the new project and new sequence, I can see the changes being made as long as the mouse is clicking on a slider. Once I release it, the effect isn't visible. I'm using Lumetri as my test effect here.
In this new sequence, once rendered, the effect is visible. If I further change the effect, the video in the program monitor returns back to the unedited video (that is, no effects visible).
Out of curiosity, I checked on what happens in Lumetri scopes when I do this. The scopes change as I move a slider, but default back to the previous position when I release it.
The original project was not upgraded from a previous version of Premiere Pro
Are you using OpenCl or Metal as the Renderer?
Try switching to the one you are not using and test.
The renderer doesn't affect the behavior in the new test project.
Another interesting thing to note: Opacity IS displaying properly in the new project, which is encouraging.
Additionally and also encouragingly, in the Project Window for the project, the thumbnail image appropriately displays the effect (I can tell because I have turned it an awful blue color).
Also potentially helpful: Render bar is green here, not red as in the old project. When I render in to out, the effect displays. Again, only up until I alter the effect.
Hmmm . . .
If you have used the Cleaner tool then your media cache should have been flushed.
Did this problem appear suddenly? Was everything OK prior to the onset of the problem?
Any new plugins etc. installed? Are you working with a media type you have used successfully before?
Maybe someone else has ideas?
Found a work around! Disabling and reenabling hardware encoding fixed the behavior in a new project. I copied the old sequence into the new one and I can start over with color correcting.
Not really sure why this worked though.