Problem Converting CV2 image to grayscale

When I run:

import numpy as np
import cv2 as cv
from matplotlib import pyplot as plt

img1 = cv.imread('the correct path',0)          # whole image
img2 = cv.imread('the correct path',0) # trainImage
gray = cv.cvtColor(img1, cv.COLOR_BGR2GRAY)

I get the error:

gray = cv.cvtColor(img1, cv.COLOR_BGR2GRAY)
cv2.error: OpenCV(4.6.0) /Users/xperience/actions-runner/_work/opencv-python/opencv-python/opencv/modules/imgproc/src/color.simd_helpers.hpp:92: error: (-2:Unspecified error) in function 'cv::impl::(anonymous namespace)::CvtHelper<cv::impl::(anonymous namespace)::Set<3, 4, -1>, cv::impl::(anonymous namespace)::Set<1, -1, -1>, cv::impl::(anonymous namespace)::Set<0, 2, 5>, cv::impl::(anonymous namespace)::NONE>::CvtHelper(cv::InputArray, cv::OutputArray, int) [VScn = cv::impl::(anonymous namespace)::Set<3, 4, -1>, VDcn = cv::impl::(anonymous namespace)::Set<1, -1, -1>, VDepth = cv::impl::(anonymous namespace)::Set<0, 2, 5>, sizePolicy = cv::impl::(anonymous namespace)::NONE]'
> Invalid number of channels in input image:
>     'VScn::contains(scn)'
> where
>     'scn' is 1


Traceback (most recent call last):
    gray = cv.cvtColor(img1, cv.COLOR_BGR2GRAY)
cv2.error: OpenCV(4.6.0) /Users/xperience/actions-runner/_work/opencv-python/opencv-python/opencv/modules/imgproc/src/color.simd_helpers.hpp:92: error: (-2:Unspecified error) in function 'cv::impl::(anonymous namespace)::CvtHelper<cv::impl::(anonymous namespace)::Set<3, 4, -1>, cv::impl::(anonymous namespace)::Set<1, -1, -1>, cv::impl::(anonymous namespace)::Set<0, 2, 5>, cv::impl::(anonymous namespace)::NONE>::CvtHelper(cv::InputArray, cv::OutputArray, int) [VScn = cv::impl::(anonymous namespace)::Set<3, 4, -1>, VDcn = cv::impl::(anonymous namespace)::Set<1, -1, -1>, VDepth = cv::impl::(anonymous namespace)::Set<0, 2, 5>, sizePolicy = cv::impl::(anonymous namespace)::NONE]'
> Invalid number of channels in input image:
>     'VScn::contains(scn)'
> where
>     'scn' is 1

I have no idea why this error is occurring and how to fix it.