problems with export audio mixdown

my export audio mixdown has suddenly just stopped working. When ever I try to mixdown I get just a blank mixdown window that does not progress in loading. Any ideas of what’s going on?

thanks!
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Is this problem occurring on multiple projects or just one specific project? Is the issue happening with only larger projects or smaller projects as well?

What specific operating system are you running and what specific Steinberg program and version number?