Welcome @soukaina.maouli
I’m sorry to hear you are having problems, but I’m really glad you wrote in for help!
CHEMFLOW Server References
- GalaxyHub Directory → ChemFlow | Galaxy Hub
- Public Galaxy Server at https://vm-chemflow-francegrille.eu/
- Resources at https://www.chemproject.org/chemflow/faq2
- Please contact us if you need help with your account at chemflow@chemproject.org
The server is running a slightly customized version of Galaxy. Web browsers change constantly and Galaxy is making adjustments constantly in response! These changes can definitely impact how complex links resolve.
I’m going to suggest a method to try that can probably help! This just worked a few minutes ago for me. 
Galaxy account confirmation steps
How do I create an account on a public Galaxy instance?
- open Chrome or Firefox or Safari, go to the server, and log into your account.
the web browser must accept cookies whenever you are using Galaxy. This is how we give you permission to see and store your own data in a persistent way!
do not use incognito or expect problems, including your results not being saved back into your account!
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open another tab in the same web browser as you used above. Copy the link from the account confirmation email and paste this into the new blank tab in your web browser. the result should be a webpage like this.
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finally, refresh your browser tab
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tip: if you are already logged into the server in another tab in the same browser, you won’t need to log in at all! Just refresh. You can also follow the Go to login page link and you’ll find yourself already logged in! -
this view
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will refresh to this view
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If this doesn’t work, then it means you have some browser setting that is not allowing cookies to be saved correctly. This is important for core functionality. Try using default browser settings to ensure your work will not be lost!
More troubleshooting
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some servers may have a setting that allows confirmation email links to expire, and instead of the registration link resolving to the green message, you’ll get a warning. You can send yourself a fresh link as shown the screenshot above. BUT do not do this unless you need to or this can keep looping around!
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if the confirmation email never arrives, try logging into your account and double checking your email address under User → Preferences.
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if you think there was a typo, update the address then send yourself a new confirmation email!
How to update account preferences? -
complex account issues will require contacting the server administrators!
Finding the contact for a Galaxy server - #6 by jennaj
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Please give this a try @soukaina.maouli! I am reviewing the contact information in the confirmation emails and will post back some updates about it, but meanwhile I think we can get you going. 
Let us know what happens! Screenshots might help if you get an unexpected message at some step.