Adding values from one dataframe to another based on two matching conditions in R

I have two dataframes below:

dput output df1:

structure(list(Location = c("1100 2ND AVENUE", "1100 2ND AVENUE", 
"1100 2ND AVENUE", "1100 2ND AVENUE", "1100 2ND AVENUE", "1100 2ND AVENUE"
), `Ivend Name` = c("3 Mskt 1.92oz", "Almond Joy 1.61oz", "Aquafina 20oz", 
"BCanyonChptleAdzuk1.5oz", "BlkForest FrtSnk 2.25oz", "BluDimndSmkhseAlmd1.5oz"
), `Category Name` = c("Candy", "Candy", "Water", "Salty Snacks", 
"Candy", "Nuts/Trailmix"), Calories = c(240, 220, 0, 215, 193, 
260), Sugars = c("36", "20", "0", "2", "32", "2"), Month = structure(c(4L, 
4L, 4L, 4L, 4L, 4L), .Label = c("Oct", "Nov", "Dec", "Jan", "Feb", 
"Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep"), class = "factor"), 
    Products_available_per_machine = c(0, 0, 0, 0, 0, 0), Units_sold = c(0, 
    0, 0, 0, 0, 0), Total_Sales = c(0, 0, 0, 0, 0, 0), Spoils = c(0, 
    0, 0, 0, 0, 0), Building = c("1100 2ND", "1100 2ND", "1100 2ND", 
    "1100 2ND", "1100 2ND", "1100 2ND"), Item = structure(c(2L, 
    2L, 1L, 2L, 2L, 2L), .Label = c("Beverage", "Food"), class = "factor"), 
    Year = structure(c(1L, 1L, 1L, 1L, 1L, 1L), .Label = "2019", class = "factor")), row.names = c(NA, 
-6L), class = c("data.table", "data.frame"), .internal.selfref = <pointer: 0x00000233561b1ef0>)

dput output df2:

structure(list(`Date Ran` = structure(c(1548892800, 1551312000, 
1553817600, 1556582400, 1561680000, 1564531200), class = c("POSIXct", 
"POSIXt"), tzone = "UTC"), Year = c(2019, 2019, 2019, 2019, 2019, 
2019), Month = c("January", "February", "March", "April", "June", 
"July"), Location = c("SEA18", "SEA18", "SEA18", "SEA18", "SEA18", 
"SEA18"), Building = c("Alexandria", "Alexandria", "Alexandria", 
"Alexandria", "Alexandria", "Alexandria"), Population = c(1177, 
1179, 1178, 1156, 1163, 1163)), row.names = c(NA, -6L), class = c("tbl_df", 
"tbl", "data.frame"))

I want to pull the pop col from DF 2 and add it to Dataframe 1 based on 'Building' and 'Month' in the order population is filled in DF2.

I tried this command using merge but the col is NULL when I execute:

df_2019_final1$Population <- df_2019_pop$Population[match(df_2019_final1$Month, df_2019_pop$Month, df_2019_final1$Building, df_2019_pop$Building)]

subset_df_pop <- df_2019_pop[, c("Month", "Building", "Population")]


updated_2019_test <- merge(df_2019_final1, subset_df_pop, by = c('Month', 'Building'))

Both produce NULLS and a blank DF

Any help would be greatly appreciated.