What is the start date? Normal rail locomotives become available after around 1925 in the Temperate climate, or 1945 in the others, and may not be available later in the game after being replaced by monorail and maglev.

Are you using any NewGRFs?

Using a vanilla download, changed the start year to 2020.

2020 may be too late

so its an ID10T error...

but you should have monorail and maglev engines available
https://wiki.openttd.org/Train_Comparison

no engines available, only cars. Can also only buy basic rails.

I will test starting game at default date in the next hour or so

Just got the chance to test....ID10T error confirmed