You are using the wrong serial number. Don;t use the HP serialnumber but generate a synology one. I can't find the link but it has been posted many times.
You can find it!
IT didn't help. Don't use the HP serial number, was generate a synology one.
set extra_initrd="extra.lzma"
set info="info.txt"
set vid=0x090C
set pid=0x1000
set sn=1230LWN464934
set mac1=00215A752564
set rootdev=/dev/md0
set netif_num=1
set extra_args_3615=''
set common_args_3615='syno_hdd_powerup_seq=0 HddHotplug=0 syno_hw_version=DS3615xs vender_format_version=2 console=ttyS0,115200n8 withefi elevator=elevator quiet'
set sata_args='sata_uid=1 sata_pcislot=5 synoboot_satadom=1 DiskIdxMap=0C SataPortMap=1 SasIdxMap=0'
set default='0'
set timeout='3'
set fallback='1'
if [ -s $prefix/grubenv ]; then
load_env
if [ -n "$saved_entry" ]; then
set default="${saved_entry}"
fi
fi
VERSION="with Jun's Mod v1.02-alpha"
search --file -s /zImage