Clients are likely not responding because your proposals are not compelling. If your proposals are anything like your profile, then they need a lot of work. First of all, you state that you are fluent in English, but your profile is very poorly written. You may need to work with someone who really is fluent in English to polish your profile and proposals. Since you are an engineer, clients aren't going to expect you to be a stellar writer, but you need to be able to effectively communicate in writing to them and understand what they are saying in their written communication to you. I would suspect your English is more conversational versus fluent.
Do a search on the forum here for profile advice and proposal advice. There is a plethora in previous threads about how to write a strong profile and how to write a compelling proposal to the client.
Kindly refer to the email sent to you by the team for more information on what changes you need to apply to your profile. If you have other questions, feel free to reply to the same ticket thread so that the team handling your case can assist you further.