Ran into similar on my HP2000.
I finally got Haiku installed and bootable on my HP2000 today.
I had many issues installing bootmanager using EFI and a GPT partition table scheme and got nowhere with GRUB2 unless you count pulling hair and stomach ulcers as advancement. I eventually broke through doing the following.
I activated Legacy Boot Mode in my BIOS prior to executing the following instructions. The way my BIOS is (as most do) is that EFI stays on and retains precedence over legacy, but Legacy is permitted when EFI is not explicit. Now, the fun starts.
1.) I wiped my drive with GParted LiveCD, created an MSDOS partition table and formatted the whole disk with a single FAT32 partition.
2.) Fired up my Haiku USB thumb-drive and installed BootManager, rebooted the system making sure the BootManager was present and operated; should attempt to start an OS only to pop up on screen again in a loop.
3.) I resized the FAT32 partition shrinking it with GParted LiveCD then created a Haiku partition.
4.) Started the Haiku thumb-drive, formatted the Haiku partition (the basic routine Be File System).
5.) Changed Parameters for the Haiku partition marking it active
(DriveSetup > Partition > Change Parameters… then check the Active Partition box)
6.) Mounted the Haiku partition and installed Haiku to the Haiku partition.
7.) Unmounted the Haiku thumb-drive.
8.) Opened a terminal and executed the following command: cd /boot/system/bin
9.) Then executed the following command: ./makebootable ‘your haiku partition label’
(Remember that if there are spaces in the haiku partition reference it has to be in quotes)
10.) Using Find entered “bootmanager” and started the application from the results list: proceeded with the bootmanager installation update (backup). Your Haiku partition should be in the menu list options that appear after completing the bootmanager backup and checked by default; complete the bootmanager update process completely then reboot and enjoy.
Hope this helps.