There are a variety of ways to ultimately arrive at a conclusion - is this a boot issue or is it a hardware issue?
I have an unorthodox suggestion that just might lead to an answer to that question - The rEFInd Boot Manager - The rEFInd Boot Manager
by Roderick W. Smith. This tool, if you download it and put it on media - or just read the information, might help you find out if this system is bootable or not. You may or may not like it as a boot loader OR a boot manager, but this tool will detect any partitions and anything bootable on your system; so if there ISN’T anything, two possible conclusions - it didn’t get installed properly or you have a hardware problem. This tool MIGHT be useful. Otherwise some good diagnostic tools might work - Rescuezilla is another system booting tool that could come in handy, Hardware diagnostics are the final thing. I try to rule out software before digging into hardware myself, but others may approach with different solutions. The other contributions offer realistic places to begin; these alternatives might find the problem in a different way.