BUG: Can't get the index location of values in df.loc
- [x] I have checked that this issue has not already been reported.

- [ ] I have confirmed this bug exists on the latest version of pandas.

- [ ] (optional) I have confirmed this bug exists on the master branch of pandas.

---

**Note**: Please read [this guide](https://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports) detailing how to provide the necessary information for us to reproduce your bug.

#### Code Sample, a copy-pastable example

```python
# Code
![Error_index](https://user-images.githubusercontent.com/26732057/128533586-cf5b54a9-ca78-4c96-84db-0ab869f1a026.png)

import pandas as pd
import numpy as np 
# import xlwings as xw
import openpyxl
# from pyxlsb import open_workbook as open_xlsb
from urllib.request import urlopen
import json
import itertools

filename = 'excel\inputFile.xlsb'
datasheet = 'Sheet1'
df = pd.read_excel(filename, sheet_name=datasheet, skiprows = 0,  engine='pyxlsb', header=None)
print('List of columns')
print(df[1])
indx_BU = df[1].loc[lambda x: x=='Busienss unit (MSK/SCL)'].index
print(indx_BU)

Problem description

I have read the excel sheet and store it in the data frame (df). if I print the column[1] values I had the value 'Business unit (MSK/SCL)'. 
But I won't get any details if I tried to get the index location of 'Business unit (MSK/SCL)'. Please do the needful.

FYR, I have attached the screenshot.

Note: Sometimes it is working even without change any code in the file. 

#### Expected Output

#### Output of ``pd.show_versions()``

<details>

python           : 3.9.0.final.0
pandas           : 1.3.1
numpy            : 1.21.1
pytz             : 2021.1
dateutil         : 2.8.2
pip              : 20.2.3
setuptools       : 49.2.1
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : 2.11.3
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fsspec           : None
fastparquet      : None
gcsfs            : None
matplotlib       : None
numexpr          : None
odfpy            : None
openpyxl         : 3.0.7
pandas_gbq       : None
pyarrow          : None
pyxlsb           : 1.0.8
s3fs             : None
scipy            : None
sqlalchemy       : None
tables           : None
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
numba            : None
None

</details>
