There was a change to the rendering options in one of the 2023 versions (and then a change back…?).
I can’t remember – it didn’t affect me so I wasn’t following too closely.
Output Override (for raster rendered viewports only was default ticked.
A number of posts have been about this with users having a similar problem to you.
Check to see if this option is ticked for you – if so untick and try to export as PDF again.