Request keeps pending

I can't understand what is wrong with the access to CDS API data because, as soon as I change a single variable in my request, the request keeps pending. I could only find one set of parameters which works. For example, the following code returns a GRIB:

c=cdsapi.Client(timeout=600, debug=True)

c.retrieve(
    'reanalysis-era5-pressure-levels',
    {
        'product_type': 'reanalysis',
        'format': 'grib',
        'variable': 'temperature',
        'time': '12:00',
        'day': '01',
        'month': '01',
        'year': '2008',
        'pressure_level': '1000'
    },'download.grib')

But if I change any parameter (let's say day=02), the request stays in pending mode. Any idea ?