Lightroom Classic images post dull on Facebook

I have tried everything, but no matter how I try to find out the problem, when the images I edit are finished in LR, I post them to FB and the colors are dull. I've put them on there full-size, resized and instead of jpgs exported, I have exported as pngs. I've gone into preferences to make the correct adjustments, but the pics are still dull and not as vibrant or bright. I realize FB compresses images, but I didn't have this problem until I upgraded to the monthly fee. My old LR6 did a great job. I am attaching pics for reference. Can anyone help, please? Thanks