In order to obtain the html code to show tweets from a specific account you may:
1. Access https://twitter.com/settings/widgets
2. Initiate session with the account from which the tweets will be shown in order to get the following screen:
3. Click on the Create New button (highlighted in the image above)
4. You will get the different options that may be configured, such as: height of the area where tweets are shown, background color, and color of links, among other things. Once the aesthetic aspects have been defined, click on the Create Widget button.
5. The HTML code generated will be presented.
This code is to be added in GXportal (from the option Design -> HTML) and afterwards associated with the corresponding GXportlet.
This will cause the tweets to be shown on your site.
If your site was already showing tweets with embedded html code and they are no longer visible, then you were probably using version 1.0 of the Twitter Api, no longer available. In your browser, if you look at the errors in the console you will find the following warning: TWITTER WIDGET: The Twitter API v1.0 is deprecated, and this widget has ceased functioning.
For the tweets to be shown you must obtain the html code for presentation again as explained above.