Please show the output of this:
grep 'RoonServer_linuxx64.tar.bz2' /boot/dietpi/dietpi-software
sed -n '/RoonServer_linuxx64.tar.bz2/p' /boot/dietpi/dietpi-software
sed -i 's|earlyaccess/RoonServer_linuxx64.tar.bz2|RoonServer_linuxx64.tar.bz2|' /boot/dietpi/dietpi-software
grep 'RoonServer_linuxx64.tar.bz2' /boot/dietpi/dietpi-software
sed -n '/RoonServer_linuxx64.tar.bz2/p' /boot/dietpi/dietpi-software
Ah lol, you used the sed to enable earlyaccess, please you the 2nd one (the one in the middle here) to disable it. It has the two pattern switched.