I work on several enterprise level applications at my current job, but I don't have clearance to share any detail about it. Nobody has. Although the applications are available publicly behind pay-wall/trial-wall, the employers don't want employees to showcase those in their portfolios. On the other hand, all the new jobs I have applied to are keen on seeing "real-world" projects. What I can show them as my portfolio (because I can't show the things I work on)?
I'm in the same boat (along with many designers.) I have yet to update my portfolio, but my thinking is to concentrate on the written story-telling aspect in your portfolio. Even if you don't have images or interactive prototypes you can show, you can write the story of your contribution.
Before you read my suggestions I want to emphasize one important thing to help prevent this conundrum in the future: ask potential employers during your interview what you can/can't show in your portfolio. A company should understand the importance of maintaining your portfolio. This will help clear up any confusion before you even accept a job offer, and hopefully give you the opportunity to keep it updated without worry.
1.) Tell the story of your contribution. What was the project's goal? What did you do on the project? What were the results? Are there metrics you can provide? (i.e., increased conversion rates by 25%, improved web performance by 50%, etc.)
2.) Draw some sketches to illustrate the narratives of your contribution. (Leave a note to say these are not representative of the UI, just graphics for visual purposes only.)
3.) Make sure the UI design of your portfolio shines. If you can't provide a lot, or any, UI examples of the work you've done in your portfolio, then make sure your portfolio is designed well and accurately reflects your style.
4.) Create a side project for fun that is representative of your capabilities. I tend to dislike this option because, personally, I'm super busy as it is. (Full-time designer + mom of two + helping my 1st-grader with virtual learning due to Covid-19.) I typically work every evening right now just to make up for lost time during the day. But this is a tough industry and if you're having trouble getting your foot in the door, you might want to give it a try. On the other hand, personal projects can be a ton of fun compared to what we're contracted to work on for clients and are an excellent opportunity to practice and expand your skillset.
5.) Recreate the work you did. Change the styles, colors, values, labels, headings, copy, or anything that might be considered intellectual property. Note: this is a suggestion but I don't know if this would still infringe on your agreement. It might be worth asking if you can.
6.) Zoom in on specific elements. Instead of showing a screenshot of an entire screen or linking to a prototype, zoom in on one specific area that you worked on to talk about only that area without displaying the entire context. You can do this with different areas of the same project. You might have to create similar redesigns to these small sections, still, as with the above suggestion for #5. And the same concerns would probably apply.
I hope these help! I'd love to check out your portfolio once you've implemented whatever solutions you come up with.
Avoid employers like that, they don't care about the people doing the work. An employer has a responsibility to nurture talent and careers, not simply squeeze employees dry and throw them away. You are allowed to talk about your experience, there is also "fair use" when it comes to copyright - if you were writing an article about the product, what could you show? You could show screenshots and video.
Work on your own projects, they will be much more rewarding long term and can provide you with experience that short-term projects never will.