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Is the Call button still disabled after you typed the phone number to call? There might be an error in what you typed. Check whether the phone number is in the right format, which is + (country code) (region code, if applicable) phone number. You must use this format for both domestic and international phone numbers.


  • The plus sign (+) at the beginning of the phone number is required. If you forget to type it, Lync Web App adds it for you.

  • To call from Lync Web App, you cannot replace the plus sign (+) with the international access code.

Here are some examples of phone number formats:

Country to call

Region to call

Phone number format

United States


+(1)(425) 555-0100 or +14255550100

United Kingdom


+(44)(20) 1234 5678 or +442912345678

People’s Republic of China


+(86)(10) 1234 5678 or +861012345678

Republic of Singapore

Not applicable

+(65) 1234 5678 or +6512345678

If you’ve entered the phone number in the correct format but you’re still seeing a disabled Call button, check if you have other issues.

Did you enter any invalid characters together with the numbers? You can only use -, (, ), and spaces.

Did you type the plus sign (+) in the middle of the number? You can only include the plus sign at the beginning of the phone number, as shown in the formats above. Anywhere else makes the number invalid.

Lync Web App ignores the spaces, (, ) and - characters you type when it interprets the phone number. These characters, although not required, are acceptable to use because they help you type the phone number in a familiar format. The interpreted number, without the extra characters, displays under Number to call. Select Call to dial the phone number.

The Call button is disabled if you type an invalid character in the phone number, or use the wrong format for the phone number. After you fix the errors in the phone number, the Call button is enabled.

If you still can’t dial the phone number, get in touch with your technical support team.

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