Grouping and Chaining data with dplyr

[JustusKilanowski]

Hello everybody,
unfortunately in the swirl course "Grouping and Chaining data with dplyr my script is not accepted. I compared it to the solutions on the internet and it seems to be correct. If my script won't be accepted I can not complete the whole course on coursera. Do you have any idea, why the script is not accepted and what to do?
Here is my script:

Compute four values, in the following order, from

the grouped data:

1. count = n()

2. unique = n_distinct(ip_id)

3. countries = n_distinct(country)

4. avg_bytes = mean(size)

A few thing to be careful of:

1. Separate arguments by commas

2. Make sure you have a closing parenthesis

3. Check your spelling!

4. Store the result in pack_sum (for 'package summary')

You should also take a look at ?n and ?n_distinct, so

that you really understand what is going on.

pack_sum <- summarize(by_package,
count = n(),
unique = n_distinct(ip_id),
countries = n_distinct(country),
avg_bytes = mean(sizes))
Thanks in advance!
Best Regards
Justus Kilanowski