Keyerror from new dataframe when plotting

Keyerror : 0 after creating new dataframe and then attempting to plot new dataframe.

Initially, the code facilitated plotting of the original dataframe. A small number of rows (~5 rows) were removed and a new dataframe was created. New dataframe displayed without issue, however upon attempting to plot the new dataframe shows a Keyerror : 0. I have attempted to resolve the issue without success.

The following is the script for the replacing, removal of missing data and new dataframe creation.

df_pre_orderset2_t = df_pre_orderset2.replace(0, np.nan)
df_pre_orderset2_top = df_pre_orderset2_t.dropna()
pd.set_option('display.max_colwidth', None)

df_pre_orderset2_to_10 = df_pre_orderset2_top.head(10)
df_pre_orderset2_top10 = pd.DataFrame(df_pre_orderset2_to_10)
df_pre_orderset2_top10

With the plot script as follows

plt.figure(figsize=(9,7))
ax = plt.gca()
x = df_pre_orderset2_top10['warning_status']
y = df_pre_orderset2_top10['count']
n = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j']
t = np.arange(10)

plt.title('Warning distribution versus order sets')
plt.ylabel('Warning count by order sets')
plt.xlabel('Warning alerts')
plt.scatter(x, y, c=t, s=100, alpha=1.0, marker='^')
plt.gcf().set_size_inches(13,8)

#scatter labels
for i, txt in enumerate(n):
   ax.annotate(txt, (x[i],y[i]))

plt.show()

This returns an in complete outline of the proposed plot and a keyerror : 0, as below.

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
~/opt/anaconda3/lib/python3.8/site-packages/pandas/core/indexes/base.py in get_loc(self, key, method, tolerance)
   3079             try:
-> 3080                 return self._engine.get_loc(casted_key)
   3081             except KeyError as err:

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()

KeyError: 0

The above exception was the direct cause of the following exception:

KeyError                                  Traceback (most recent call last)
<ipython-input-161-0cc4009cf4a7> in <module>
     16 #scatter labels
     17 for i, txt in enumerate(n):
---> 18     ax.annotate(txt, (x[i],y[i]))
     19 
     20 plt.show()

~/opt/anaconda3/lib/python3.8/site-packages/pandas/core/series.py in __getitem__(self, key)
    851 
    852         elif key_is_scalar:
--> 853             return self._get_value(key)
    854 
    855         if is_hashable(key):

~/opt/anaconda3/lib/python3.8/site-packages/pandas/core/series.py in _get_value(self, label, takeable)
    959 
    960         # Similar to Index.get_value, but we do not fall back to positional
--> 961         loc = self.index.get_loc(label)
    962         return self.index._get_values_for_loc(self, loc, label)
    963 

~/opt/anaconda3/lib/python3.8/site-packages/pandas/core/indexes/base.py in get_loc(self, key, method, tolerance)
   3080                 return self._engine.get_loc(casted_key)
   3081             except KeyError as err:
-> 3082                 raise KeyError(key) from err
   3083 
   3084         if tolerance is not None:

KeyError: 0