I linked my PR application on gckey. In gckey homepage, there is an option to add existing application. You can find your application after getting eCOPR. I consulted this video, you have to be careful with bold letters,place of birth name has to be exact, including white spaces. It took me 3to 4 attempts to get it to work. Search below the text on youtube and look at this video. Sometimes posts are removed if i put links, so just copy and put this on youtube (text given below)
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How to link PR Card with CIC Account | Status of your Canada PR card application in IRCC account"