Rendered movie - does not open

Hello,
I've used DaVinci Resolve for private videos more than 10 times already creating short 10-20 min long videos no problem.
This time I've created a 90minutes long video DaVinci Resolve free version.
When I export it in deliver I already tried 2 ways.
Either mp4 or mov. Using H.264 codec. File that I export has ~9 GB. But when I try to open exported file with any of the programs to watch it - it just doesn't work. Might someone have an idea what is the issue? I can provide more information if needed, just ask.
I've used DaVinci Resolve for private videos more than 10 times already creating short 10-20 min long videos no problem.
This time I've created a 90minutes long video DaVinci Resolve free version.
When I export it in deliver I already tried 2 ways.
Either mp4 or mov. Using H.264 codec. File that I export has ~9 GB. But when I try to open exported file with any of the programs to watch it - it just doesn't work. Might someone have an idea what is the issue? I can provide more information if needed, just ask.