Failed to deploy OVA

I am trying to deploy cnMaestro on Prem for the first time and I was stuck on a problem.
Tried to load cnmaestro-on-premises_2.3.0-r28_amd64.ova for couple of times to VM but both failed. The error message says line 1 is invalid (see attached screen shot).
I tried the previous version cnmaestro-on-premises_2.2.0-r60_amd64.ova but it failed as well with the same error.
I finally tried the older cnmaestro-on-premises_1.6.1-r10_amd64.ova and it deployed successfully.
The instruction from Cambium is very simple but am I missing something here?
VMware: VSphere 5.5
I appreciate your answer/feedback.

That's because your vmware 5.5 doesn't support SHA256 hash.

You need to convert that OVA from sha256 to SHA-1, using ovftool.

Something like:

ovftool.exe --shaAlgorithm=SHA1 cnmaestro.ova cnmaestrosha1-SHA1.ova

command line from the folder where you have your ova, of course.

PS check my command, i'm not sure about the syntax.