Stuck on AmiShimTimerBoostExit

I'm trying to boot High Sierra on a laptop. After selecting OpenCore external, the screen flashes with text and then nothing happens. The last three entries in the debug log are the following:

47:961 01:024 OCSMC: SmcReadValue Key 4D535463 Size 1

48:001 00:039 OCSMC: SmcReadValue Key 4D534163 Size 2

48:037 00:035 AmiShimTimerBoostExit changed current period to 549254

What should I do?

submitted by /u/flooatinghoodie
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