Going into my 23rd month soon, and still no invite. I tried every possible contact method, my only resort now is the writ of mandamus. Costly, but I ran out of options.
Hello, when my application was going 13 months, I went to MP (Member of Parliament) and asked their advise. From there, I learned why my application was delayed tho I had a hunch already and I brought all the documents needed to support my claim.
Google the address of the MP in your area and ask for their help.
To me, after asking for help, my application started to move again.
My timeline:
March 2018 - application
May 2018 - In Process
April 2019 - went to MP
June 4 - CIC mailed about additional document (cause of delay)
June 2019 - Got my test invite
July 10 - Took the test
Aug 8 - invitation to attend ceremony
Sept 5 2019 - My oath taking
Goodluck!