Project won't save

I have a 1.5 hour long, 2 tracks project, with default setting, but the project won’t save because it says the disk I’m trying to use is full, but there’s over 7 GB of free space on that disk, which i my laptop SSD hard drive.

2 tracks (each perhaps stereo ? - making it 4 tracks in total) and each 1.5 hours long, could quite easily exceed 7 GB.
Do you have another drive you could try saving to?