How to fix Google Earth Engine Error: 'FeatureCollection (Error) Image.sample: Unable to find a crs.'

Question

I am trying to make a random forest classifier for mangroves on an island in the Philippines. I have already produced the desired outcome for dates in 2019 using exactly the same code, but I need the dates changed to ones in December 2021.

// cloud filtering 
function maskS2clouds(image) {
  var cloudBitMask = ee.Number(2).pow(10).int();
  var cirrusBitMask = ee.Number(2).pow(11).int();
  var qa = image.select('QA60');
  var mask = qa.bitwiseAnd(cloudBitMask).eq(0).and(qa.bitwiseAnd(cirrusBitMask).eq(0));
  return image.updateMask(mask);
}

// rename bands
function renameS2bands(image){
  return image.rename('B', 'G', 'R', 'NIR', 'SWIR', 'SWIR2', 'QA60')
}

// load Sentinel-2 TOA reflectance data.
var s2collection = ee.ImageCollection("COPERNICUS/S2_SR_HARMONIZED")
              .filterDate('2021-10-01', '2021-12-15')
              .filter(ee.Filter.lt('CLOUDY_PIXEL_PERCENTAGE', 10))
              .filterBounds(geometry)
              .select('B2', 'B3', 'B4', 'B8', 'B11', 'B12', 'QA60')
              .map(maskS2clouds)
              .map(renameS2bands);

//Reduce the first collection (median reducer in this case)
var s2_median = s2collection.median()

// load the pre-computed Sentinel-2 composite as input
var input = s2_median;

// define a region in which to generate a sample of the input
var region = geometry;

// make the training dataset
var training = input.sample({
  region: region,
  scale: 20,
  numPixels: 40
});

// print training (feature collection)
print(training)

The error is: FeatureCollection (Error) Image.sample: Unable to find a crs.

My geometry variable is a geometry drawn around an island in the Philippines. Any help would be much appreciated.