If you are facing issue with upwork app like connection failed, not starting or want to install new upwork app

Please follow this:

https://support.upwork.com/hc/en-us/articles/211064108-Linux-Troubleshooting-for-Upwork-Team-App

and again you are facing same issue then please follow below commands:

If your package libnss3 was upgraded to 3.21 version and above, it may cause issues so please do the following:

64 bit:

sudo dpkg --force-all -r libnss3
wget http://security.ubuntu.com/ubuntu/pool/main/n/nss/libnss3_3.19.2.1-0ubuntu0.15.10.2_amd64.deb
sudo dpkg -i libnss3_3.19.2.1-0ubuntu0.15.10.2_amd64.deb
If this does not work please also try:

http://security.ubuntu.com/ubuntu/pool/main/n/nss/libnss3_3.19.2.1-0ubuntu0.15.04.2_amd64.deb

32 bit:

sudo wget http://security.ubuntu.com/ubuntu/pool/main/n/nss/libnss3_3.19.2-1ubuntu1_i386.deb
sudo dpkg -i libnss3*