Version 2.0.0 of the readr package was released July 20, 2021. This new version causes stackByTable() to error out in neonUtilities 2.1.0 and earlier. This error also affects loadByProduct() and stackFromStore(), both of which are wrappers for stackByTable(). stackEddy() should be unaffected, as should stackFromStore() when used as a wrapper for stackEddy().
To avoid this problem, do not update readr to 2.0.0. If you encounter an error in data stacking using neonUtilities, try reverting to readr 1.4.0.
A new version of neonUtilities that resolves this issue will be released as soon as possible. An update will be posted when the new version is available.