It seems there are some problems with permissions, you can try this command to allow binding obfs4 below ports 1024.
sudo setcap cap_net_bind_service=+ep /usr/bin/obfs4proxy
The next thing you have to check is the binary file of the package /usr/bin/obfs4proxy, permissions by default should be 755 (rwxr-xr-x). It means readable and executable by everyone. You can view permissions by doing the command ls -la /usr/bin/obfs4proxy
If permissions are wrong, you can do this command to set the right permissions on the file :
sudo chmod 755 /usr/bin/obfs4proxy
Then restart the tor service and check the logs again to see if its working 