Well, I found that solution here on maemo org. Here is the link https://wiki.maemo.org/Community_SSU/Installation_FAQ

I did perform these commands as I occurred such issue upon installation attempt. Please see the quote below.

In the past I did these actions with those commands on my previous Nokia's N900 and it was ok also installation were completely without any problems and devices were working fine, seriously I did this and it worked fine.

From time to time I buying another one nokia n900 when I miss so much the maemo and then I occurring every time another issue which comes with another bought Nokia n900, which drive me to crazy. Seriously this is not a random action, this is something which I did in the past with different bought Nokia N900 and it was fine. Then I playing with the device getting boring and selling then buying again and here we have another odds problems with CSSU installation.

Regarding the Maemo OS reflash, is this possible to do in these days when the main PC machine running latest Windows 10 OS, where I can find the proper OS ISO for the N900 which I bought two days ago. Is this even possible to do.

Well, I have an flasher 3.5 on my OSX laptop which I used it for flashing the Nokia N9 about two years ago as there was an outdated MeeGo version. I did this and I did nit brick the N9. Will this flasher work with the N900? If yes, that's mean I need to find the proper maemo OS version Only?
Would any one suggest me, what kind the maemo os version I will need to download. Please.