Affinity Photo PSB Question

[PocketDucky]

I transitioned away from photoshop and Adobe for many reasons that many of you I'm sure already know

I'm a tabletop roleplaying game, game master. I've worked for many years on a Google Earth-style world map in Photoshop. It became an incredibly big file because I had ambition to print it out to something like 12 feet by 6 feet at a high resolution. So eventually to accommodate the file size, the file went from a .PSD to a .PSB. Affinity thankfully imports this file format too. However it crashes open apps every time I open it in Affinity Photo. Other files work fine.

The file is 3.5 gb/ 18,000x18,000 px for reference. What can I do? There's years of work in that file, and I'm unwilling to go back to photoshop. 

Edited January 4 by PocketDucky

[Komatös]

Hello @PocketDucky and welcome to the forums.

The question becomes a quiz without any further information about the hardware used.

Spontaneously, I would conclude that there is not enough RAM.

[Hangman]

Hi @PocketDucky and another warm welcome to the forums,

Just to add to @Komatös's feedback... If you're willing to provide a download link to the file others in the forum can see whether they are able to open the file to determine whether it is, as mentioned a RAM issue or whether there is any element of file corruption with the .PSB file preventing the file from being opened...