With ConTeXt ver: 2021.04.28 18:39 LMTX fmt:
2021.4.29 int, I am now getting the following error on compiling with
files that were OK previously. Is there something that I need to change?
The error is caused by the fallback font for math but you have create a
minimal example because I'm unable to reproduce it (copy all font
settings to a new document and run ConTeXt).
Can you also check if the font files are found by ConTeXt: