Tap holes will dry out, but it takes a lot longer than a few days for that to happen!
What's the weather been like since Sunday? If it's either been 1) above freezing the whole time - day and night, or 2) below freezing the whole time - day and night, that's the likely cause. The sap flows good when it freezes at night and thaws during the day.
Good luck!
Dan
-15 years sugaring and counting - hoping to create a tradition my kids will always remember
-400 taps, mostly buckets (Silver Maples + a few Boxelders just for the heck of it)
-Custom-built 2x6 evap with Smoky Lake Maple raised flue, boiling in dad's old farm granary, now converted to sugar shack
-Cobbled-together RO with XLE4040 membrane
-New in 2021: experimenting with 3/16 tubing & a Shurflo pump.