OK, good. In this comment I asked you to modify your .env file to point to the new certificate paths, but according to your output in this comment it looks as if you have both options active in the .env file. Please check the first mentioned comment again and verify that your .env file looks similar in the relevant section. A # sign in front of a line means that the line is NOT active. You can only have one active line starting with CERT_PATH and one with KEY_PATH and they should look like this:
CERT_PATH=./certs/etc/letsencrypt/live/${DOMAIN}/fullchain.pem
KEY_PATH=./certs/etc/letsencrypt/live/${DOMAIN}/privkey.pem
Then please run the following commands to make sure those files are actually there, are readable and in the right format:
DOMAIN=$(awk -F= '$1~/^DOMAIN/ { print $2 }' .env); CERT=$(awk -F= '$1~/^CERT_PATH/ { print $2 }' .env | sed 's/\${DOMAIN}/'$DOMAIN'/'); find $CERT; file $CERT; ls -l $CERT; head -3 $CERT
DOMAIN=$(awk -F= '$1~/^DOMAIN/ { print $2 }' .env); CERT=$(awk -F= '$1~/^KEY_PATH/ { print $2 }' .env | sed 's/\${DOMAIN}/'$DOMAIN'/'); find $CERT; file $CERT; ls -l $CERT; head -3 $CERT
The first line will validate the CERT_PATH, the second line will validate the KEY_PATH.
The output should look similar to this:
# for CERT_PATH
./certs/etc/letsencrypt/live/mattermost.mywebsite.com/fullchain.pem
./certs/etc/letsencrypt/live/mattermost.mywebsite.com/fullchain.pem: symbolic link to ../../archive/mattermost.mywebsite.com/fullchain1.pem
lrwxrwxrwx 1 root root 46 Aug 28 21:40 ./certs/etc/letsencrypt/live/mattermost.mywebsite.com/fullchain.pem -> ../../archive/mattermost.mywebsite.com/fullchain1.pem
-----BEGIN CERTIFICATE-----
MIIFKTCCBBGgAwIBAgISBHrIWlZDgcBKF1xVx1ZAyRvjMA0GCSqGSIb3DQEBCwUA
MDIxCzAJBgNVBAYTAlVTMRYwFAYDVQQKEw1MZXQncyBFbmNyeXB0MQswCQYDVQQD
# for KEY_PATH
./certs/etc/letsencrypt/live/mattermost.mywebsite.com/privkey.pem
./certs/etc/letsencrypt/live/mattermost.mywebsite.com/privkey.pem: symbolic link to ../../archive/mattermost.mywebsite.com/privkey1.pem
lrwxrwxrwx 1 root root 44 Aug 28 21:40 ./certs/etc/letsencrypt/live/mattermost.mywebsite.com/privkey.pem -> ../../archive/mattermost.mywebsite.com/privkey1.pem
-----BEGIN PRIVATE KEY-----
MIIEvwIBADANBgkqhkiG9w0BAQEFAASCBKkwggSlAgEAAoIBAQCi0owRzEjnm+1x
Dc0gZml7tZPDWi6vgLFz/jiyVzLumKNhRmvmg6UtL+jZiC0mbM9FZW64l8a5PlZl
If this is the case, you can try to docker compose ... up again (without the -d flag) and let me know if there are any other error messages on the screen.