This happens if either the Standard Calendar (or any resource's calendar that is on the team) has more than 51 characters. When you attempt to open the project, you first see a Microsoft Project message "An Import error occurred. The element in the element with = 1 (Or ID of the respective calendar) has invalid data. The calendar name does not exist. Click a calendar in the list, and then press Enter." Once you click OK to the message, the project opens blank with no data. 

STEPS TO REPRODUCE

1. In Clarity, create a calendar with more than 51 characters:
   • Go to Administration->Project Management ->Base Calendars
   • Click ‘New’
   • In the Calendar Name field, enter a name with more than 51 characters (Example name: Calendarcharacterlengthissuewithmspnewdrivertest1234)
   • Click the check box next to Standard to make it the Standard calendar
   • Click ‘Save’
2. Create a new project in Clarity with one task (No tasks are needed to reproduce this issue, this is to show the effect of the project also being blank in MSP)
3. Attempt to open the export the project from Clarity to MSP 

Expected Results: The project opens successfully with the one task shown on the project 
Actual Results: When you attempt to open the project, you first see a Microsoft Project message "An Import error occurred. The element in the element with = 1 (Or ID of the respective calendar) has invalid data. The calendar name does not exist. Click a calendar in the list, and then press Enter." Once you click OK to the message, the project opens blank with no data. 

Notes: 

• You can reproduce this issue with calendars that are not the standard by associating a resource on the project team with that calendar in 14.4 (In 15.1/15.2, you can't always reproduce the issue unless the Calendar is the Standard Calendar in the application which appears to be because of a separate calendar defect, DE32693, that was introduced in 15.1. In 15.1 and 15.2, the resource's calendar with the issue may not always be exported to MSP because of DE32693, so then you won't see the effects of the issue at the resource level in that case)
• If this project is a sub project of another project, when you attempt to open the master project associated with the problem project, you'll see the following:

• • A popup window opens looking for the file in the MSP Bin folder "Example: Program Files (x86) -> CA -> PPM - CA PPM MSP Interface -> Bin".
  • A message at the top of the window states "Cannot find inserted project - ...". When you click 'Cancel' to the message it takes you to just a list of the sub projects, and no actual tasks for the projects. 

Reference Unable to open a master project in MSP (popup window appears

• Symptoms in the MSP Legacy driver: The project opens successfully, but if a resource on the team is assigned to the calendar, when you open the project in MSP, the calendar is not exported. Instead, the resource is assigned to the Standard calendar. Impact: Any of the calendar settings for the calendar the resource is assigned to in MSP that are not in the Standard calendar are not carried over and considered in MSP (example, any non-working days set on the >51 character calendar not on the Standard calendar are not carried over). 

MSP New Driver

This issue is caused by a limitation with Microsoft Project. MSP only allows calendar names with 51 characters or less. Note: this limitation also applies to all view names as well in MSP.

Steps to Reproduce in MSP Standalone:

1. In MSP, go to File->Organizer->Calendars tab
2. Select any calendar and click the 'Rename...' button
3. In the New Name text field, attempt to add a calendar name with more than 51 characters (IE: Calendarcharacterlengthissuewithmspnewdrivertest1234)

Results: It only inputs the first 51 characters of the name, so in the example above, the last number (4) is cut off from the name.

Reduce the length of the calendar name to be less than 51 characters:

1. In Clarity, go to Administration->Project Management ->Base Calendars
2. Click on the calendar with the issue
3. Click on the ‘Edit Calendar Properties’ tab
4. In the Calendar Name field, change the name of the calendar to be less than 51 characters
5. Click ‘Save’ 

Reference Some Resource Calendars do not show in MSP for more information on DE32693

Reference Unable to open a master project in MSP (popup window appears)